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Electronics Technology
Section 1: Learning Objectives.
- Identify the different properties between Conductors,
Insulators, and Semiconductors.
- Translate the basics of time, weight, distance and
electrical units.
- How to simplify, and round large numbers, recognize
and use Scientific notation while using its proper name
and symbol.
- Be aware of the differences in a digital and analog
multi-meter.
History of the discovery of
Electricity



In popular literature Benjamin Franklin is
often credited with the discovery of
electricity.
However, it was known at least as early as
600 BC that amber (fossilized sap) would
attract dust and other small particles after
being rubbed with wool.
This property was called electricity after
the Greek word for amber, elektron.
How Electricity flows in:



Conductors
Elements that have fewer than four valence electrons are called
metals. With fewer than four valence electrons it is relatively easy
for atoms to exchange electrons. Copper, for example, has only
one electron in its valence shell.
Insulators
Elements with more than four valence electrons are called nonmetals. The electrons in non-metals form tight bonds with
electrons of nearby atoms, locking them in place in the mass of
material. Therefore, non-metals are generally non-conductors.
Actually, most non-metals are not well suited for use in electrical
circuits since they are either liquid or gaseous at normal
temperatures and pressures. Because of this, most insulators are
made of compounds such as glass, ceramic or plastic.
Semiconductors
Elements that have four valence electrons, the halfway point
between conductors and insulators, are called semiconductors.
They are basically insulators but can be doped with impurities that
cause them to act as conductors.
Conductors and Insulators
Semiconductors
Silicon
Germanium
Direction of Electrical Flow

Electron Flow
 Electron flow considers the actual flow of negatively
charged electrons-from negative to positive-as current
flow. It is more difficult to visualize than conventional
flow because the current seems to flow from a low
pressure (negative) to a high pressure (positive). In
schematic diagrams the current flows against the arrows
in semiconductor devices.

Conventional Flow
 Conventional flow considers flow of an imaginary
(positively-charged) fluid from positive to negative. It is
easier to visualize than electron flow because the
current flows from a high pressure (positive) to a low
pressure (negative). In schematic diagrams the current
flows in the direction of arrows in semiconductor devices
The Elements of Electricity





Voltage
Current
Resistance
Types of Current: AC and DC
Circuits
Closed
Open
Short
VOLTAGE



Because like charges repel and unlike charges
attract, electrons will move from the negative
source to the positive end.
The applied force that causes the electrons to
flow is called voltage (after the scientist
Alessandro Volta) or electromotive force (emf).
We give it the symbol or ℰ in equations. Voltage
is measured with a voltmeter or multimeter and
is the potential difference between two points in
a circuit. The basic unit is the volt (V).
CURRENT


Current is a flow of electrical charge
carriers, usually electrons or
electron-deficient atoms.
The common symbol for current is
the uppercase letter I. The standard
unit is the ampere, symbolized by A.
RESISTANCE


Opposition of a circuit to the flow of
electric current. Resistance is
measured in Ohms.
Resistance is represented by the
Greek symbol- Omega Ώ.
Forms of Current

There are 2 types of current
The form is determined by the
directions the current flows through a
conductor

Direct Current (DC)
Flows in only one direction from
negative toward positive pole of source

Alternating Current (AC)
Flows back and forth because the poles
of the source alternate between positive
and negative
The Water Analogy


Resistance is a
property that
slows the flow of
electrons.
Using the water
analogy,
Resistance is
anything that
would slow the
flow of water
through a pipe
Measuring Electricity

The scientific world uses the International
System of Units (SI units) to measure things.
The International System of Units starts with
three basic units:
 The kilogram, the meter and the second. Every other
unit is derived from these three basic units.

For example:
 To know what a volt is, we have to know what a watt is.
 To know what a watt is, we have to know what a joule
is.
 To know what a joule is we have to know what a meter
and a Newton are.
 Finally, to know what a Newton is we have to know
what a kilogram a meter and a second are.
Base Units


Kilogram (kg) - The
kilogram is the unit of
mass that is equal to
the mass of the
international prototype
of the kilogram.
The kilogram is a
particular cylinder of
platinum-iridium alloy
that is preserved in a
vault at Sevres, France,
by the International
Bureau of Weights and
Measures.
Base Units

Second (s) - The
second is the
duration of
9,192,631,770
periods of the
radiation
corresponding to
the transition
between the twohyperfine levels of
the ground state of
the cesium 133
atom.
Base Units


Meter (m) - The
meter is the length of
the path traveled by
light in vacuum
during a time interval
of 1 / 299,792,458 of
a second.
This speed is a
definition, not a
measurement.
Derived Non Electrical Units

Newton (N)
The Newton is that force which gives to
a mass of 1 kilogram an acceleration of
1 meter per second per second (1m/s2).

Joule (J)
The joule is the work done when the
point of application of I Newton is
displaced a distance of 1 meter in the
direction of the force.
Derived Electrical Units

Ampere (A)
ampere (amp) is that constant current which,
if maintained in two straight parallel
conductors of infinite length, of negligible
circular cross section, and placed 1 meter
apart in vacuum, would produce between
these conductors a force equal to 2x10-7
Newton per meter of length.

Coulomb (C)
The coulomb is the quantity of electricity
transported in 1 second by a current of 1
ampere.
Derived Electrical Units Cont’d

Watt (W)
The watt is the power which gives rise to the
production of energy at the rate of 1 joule per
second.

Volt (V)
The volt is the difference of electric potential
(electromotive force) between two points of a
conducting wire carrying a constant current of
1 ampere, when the power dissipated between
these points is equal to 1 watt.
Derived Electrical Units (Cont’d)

Ohm(W)
ohm is the electric resistance between two
points of a conductor when a constant
difference of potential of 1 volt, applied
between these two points, produces in this
conductor a current of 1 ampere, this
conductor not being the source of any
electromotive force.

Farad (F)
The farad is the capacitance of a capacitor
between the plates of which there appears a
difference of potential of 1 volt when it is
charged by a quantity of electricity equal to 1
coulomb.
Derived Electrical Units (Cont’d)

Henry (H)
The Henry is the inductance of a closed circuit
in which an electromotive force of 1 volt is
produced when the electric current in the
circuit varies uniformly at a rate of 1 ampere
per second.
SI Electrical Units Commonly
Used with Electronics
Unit
Unit
Symb
ol
Formula
Symbol
Electrical potential difference,
electromotive force
volt
V
E
Electrical resistance
ohm
W
R
Electrical conductance (1 / R,
formerly known as mho)
siemens
S
G
Electrical current
ampere
A
I
hertz
Hz
ƒ
coulomb
C
q
Capacitance
farad
F
C
Inductance
Henry
H
L
Impedance
ohm
W
Z
Name
Frequency
Electrical charge, quantity of
electricity
SI PREFIXES EXPLAINED


Working in electronics often requires working with very large
and very small numbers, such as thousands of ohms or
millionths of farads. To simplify writing these numbers,
prefixes are use to represent multipliers. For example,
1,000 ohms is expressed as 1-kilo ohm, 1k ohm, or just 1k.
A capacitance of .000001 farad is expressed as 1
microfarad, 1mF or just 1m.
Very large or very small numbers can be expressed in
scientific notation. Scientific notation expresses the number
as the three most significant digits (rounded) with a decimal
point placed after the first digit followed by “X10” and an
exponent (the exponent tells how many places to move the
decimal point to get it back to its original place). For
example, 1,000 is expressed in scientific notation as
1.00X103 (pronounced “one point zero zero times ten to the
third”) and 1,258,432 is expressed as 1.26X106. Very small
numbers are expressed with a negative exponent. For
example, 0.001 is expressed as 1.00X10-3 and
0.000,001,258,432 is expressed as 1.26X10-6.
SI Prefixes Commonly used with
Electronics
SI Prefixes Commonly Used in Electronics
Name
Symbol
Multiplier
Scientific Notation
Tera
T
x 1,000,000,000,000
1.00X1012
Giga
G
x 1,000,000,000
1.00X109
Mega
M
x 1,000,000
1.00X106
kilo
k
x 1,000
1.00X103
milli
m
x .001
1.00X10-3
micro
m
x .000,001
1.00X10-6
nano
n
x .000,000,001
1.00X10-9
pico
p
x .000,000,000,001
1.00X10-12
How could we express 20,950?
By using the prefix
chart we could
simply move the
decimal in 20,950.
over 3 places to
the left and we end
up with 20.95k.
Lets try a few more…
128M W
=128,000,000 W
.0000052
=5.2µ
200G
=200,000,000,000
Review of Section 1
Q.
What constitutes a Conductor,
Insulator, and a Semiconductor?
A. A conductor less than 4 valence electrons, an insulator has more
then 4 electrons and a semiconductor have exactly 4 electrons
and can be manipulated to act as a conductor.
Q.
What is different between Electron flow
and Conventional flow?
A. Electron flow goes negative to positive for current flow,
Conventional goes positive to negative.
Q.
What is Conductance?
Q.
How do you calculate Conductance?
A. Conductance is the opposite of resistance: the measure of
how easy is it for electrons to flow through something.
A. 1/Resistance.
DC CIRCUITS
Section 2: Learning Objectives






Describe wire gauges and calculate color
coded resistors.
Understand Kirchhoff’s Voltage law and
Kirchhoff’s Current Law.
Determine resistor values by using color
code.
Evaluate a basic circuit and determine
wither it is series, or parallel or seriesparallel.
Learn to apply Thevenins Theorem to
series-parallel circuits.
Know and understand Ohm’s Law.
Resistors


The resistor is one of the basic
components in electrical circuits. Resistors
are used where the resistance of the
circuit needs adjustment, typically for
limiting the electrical current between two
nodes.
The majority of resistors in a circuit have
fixed resistance values, however
potentiometers may be used to allow
adjustment of the resistance. One typical
application of potentiometers is volume
control in audio players.
Resistors

Function of resistors
 The function of a resistor in a circuit is
described by Ohm's law and depends upon
three variables:
1.
2.
3.

The resistance of the resistor,
The voltage difference between its poles
The flow of electrons (current) through the resistor.
If two of the three are known, the third can easily
be calculated.
Resistors are not polarized, meaning that
they can be inserted into a circuit either
way around.
Resistance Defined

Resistance is the impediment to
the flow of electrons through a
conductor
Resistance is Friction to moving electrons
Friction generates heat
All materials exhibit some resistance, even
the best of conductors

Resistance is measured in Ohm(s)
From fractions of Ohms to millions of Ohms
Resistance Example



If you rub the palms of your hands together, you will realize that your
hands do not move freely across each other. You will also note that
while rubbing your hands back and forth, heat is generated. This heat
is generated from the friction between your palm surfaces resisting
the movement of your hands. Since your palms are resisting the
kinetic energy from the movement of your hands, the resistance is
converted to heat..
The same thing happens as electrons try to move through a conductor
or other material. The electrons run into things as they move, and
each collision causes the electron’s movement to be impeded in some
way, and the resulting loss of kinetic energy is converted into heat. In
the majority of cases in electronics, this heat is an undesired
byproduct. In other cases, the heat is desirable as is the case with a
stove top. In still other cases, the generated heat must be moved
away from the electronic device to prevent damage to other
components. A good example of this would be the fans in a computer.
In summary, resistance is friction toward moving electrons. All
materials provide some level of resistance. The unit of resistance is
the Ohm. Resistance measurements can be incredibly small to
incredibly large.
Wire and Resistance


Wire is usually used to simply
carry electricity from one point to
another. Electrical wire is usually
made of copper but aluminum
and even silver and gold are
sometimes used.
Notice that as the diameter of
the wire increases the gauge
number decreases. The electrical
resistance decreases with larger
diameter wire but increases with
length.

The resistance also increases
with temperature.

An ohmmeter is used to test the
resistance or continuity of a wire.
Resistor Types





Fixed Value
Variable value
Composite resistive material
Wire-wound
Two parameters associated with
resistors
Resistance value in Ohms
Power handling capabilities in watts
Resistor Types Defined


Fixed Value- A fixed-value resistor
has a series of coloured bands
around its body, which signifies the
resistor's value and tolerance.
Variable- The resistance value of a
variable resistor can be varied
between an upper and lower limit.
Reading Resistor Color Codes
Ohm’s Law
Ohms Law states that the direct current flowing in a conductor is
directly proportional to the potential difference between its ends.
Ohms Law is usually formulated as E = IR, where:
E is the potential difference, or voltage,
I is the current, and
R is the resistance of the conductor.
Resistors in Circuits
Series

Looking at the
current path, if
there is only
one path, the
components
are in series.
Resistors in Circuits
Series




The main distinction between series and
parallel circuits is how many paths the
current has available to complete the
course from the negative pole of the
power source to the positive pole.
In this diagram, all the current from the
battery must pass through both resistors.
Therefore this circuit a series circuit.
At this point you need to develop the
concept of equivalent resistance.
Equivalent resistance is what the total
resistance would be if you substituted a
single resistor the resistors that make up
the circuit.
In this case, if the two resistors were to be
combined and replaced with a single
resistor that had the same resistance, that
single resistor would be the equivalent
resistor.
Calculating Resistors in Series




It is easy to calculate the equivalent resistance of
resistors in series.
Total Resistance is simply the sum of all the
resistances.
For example, if R1 is 400 ohms and R2 is 100
ohms, then the equivalent resistance would be
500 ohms.
Another example, if R1 is 50 ohms, R2 is 20k
ohms (remember 20k ohms = 20,000 ohms), and
R3 is 900 ohms, the equivalent resistance would
be 20,950 ohms or 20.95k ohms.
Adding Resistors in Series

For the following exercise, use the
series formula for finding total
resistance
RT = R1 + R2 + R3 + R4….
Remember, Resistance is measured
in Ohms and is represented by the
Greek symbol Omega Ω.
Resistors in Circuits
Parallel



If there is more than
one way for the
current to complete its
path, the circuit is a
parallel circuit.
In this case, there are
two possible paths.
The electrons can go
through the left most
resistor or the right
most resistor.
Since there is more
than one path option,
this is a parallel circuit.
Resistors in Circuits
Parallel




By the very nature of a parallel
circuit, the equivalent resistance
will be less than any of the single
resistors that make up the circuit.
This property makes sense if you
think about it. Referring back to
the water analogy. If there is
more than one hose for the water
to flow through, each path has a
relatively narrow hose
(resistance).
Then what the water sees as it
approached the hose openings is
not the narrow opening of just one
hose, but the sum of all the
opening in the hose, which would
make it appear that there is one
large opening to go through.
That one large opening is like
seeing one lower resistance path
than the individual hose openings.
Total Resistance in Parallel Circuits
R1
R2
RT?
100 Ω 200 Ω
420 Ω 500 Ω
210 Ω 610 Ω
360 Ω 25 Ω
12k Ω 2k Ω
15M Ω 12M Ω
20m
Ω
20m
Ω
R1
R2
Total Resistance in Parallel Circuits
R1
R2
RT?
100 Ω 200 Ω 66.67 Ω
420 Ω 500 Ω 228.26Ω
210 Ω 610 Ω 156.21Ω
360 Ω 25 Ω
23.4Ω
12k Ω 2k Ω
1.7kΩ
15M Ω 12M Ω 6.7MΩ
20m
Ω
20m
Ω
10mΩ
R1
R2
If the path for the
current in a
portion of the
circuit is a single
path, and in
another portion of
the circuit has
multiple routes,
the circuit is a
mix of series and
parallel.
Series

Series
Resistors in Circuits
Combination Parallel and Series
Parallel
Resistors in Circuits
Parallel and Combination

Let’s start with a
relatively simple
mixed circuit.
Build this using:
 R1 = 330
 R2 = 4.7K
 R3 = 2.2K
R1
R2
R3
Resistors in Circuits
Combination

Take the
parallel
segment of the
circuit and
calculate the
equivalent
resistance:
R2 R3
RE 
R2  R3
R1
R2
R3
Resistors in Circuits
Combination


We now can look at
the simplified circuit as
shown here. The
parallel resistors have
been replaced by a
single resistor with a
value of 1498 ohms.
Calculate the
resistance of this
series circuit:
R1  R2,3
R1
R2,3 = 1498
Resistors in Circuits
Combination



=
=
=
=
330
1K
2.2K
4.7K
Series
R1
R2
R3
R4
R1
R2
R4
R3
Parallel

In this problem, divide
the problem into
sections, solve each
section and then
combine them all back
into the whole.
Series

Resistors in Circuits
Combination

Looking at this
portion of the
circuit, the
resistors are in
series.
 R2 = 1k-ohm
 R3 = 2.2 k-ohm
R2,3  R2  R3
R2
R3
Resistors in Circuits
Combination

Substituting the
equivalent
resistance just
calculated, the
circuit is simplified
to this.
 R1 = 330 ohm
 R4 = 4.7 k-ohm
 R2,3 = 3.2 k-ohm

Now look at the
parallel resistors
R2,3 and R4.
R1
R2,3
R4
Resistors in Circuits
Combination

Using the
parallel
formula for:
 RE = 3.2 kohm
 R4 = 4.7 kohm
R2,3, 4 
R2,3 R4
R2,3  R4
RE
R4
Resistors in Circuits
Combination

The final
calculations involve
R1 and the new
RTotal from the
previous parallel
calculation.
 R1 = 330
 RE = 1.9K
RTotal  R1  R2,3, 4
R1
RTotal
Resistors in Circuits
Combination
R1 = 330 ohm
RTotal = 2,230
R2 = 1 k-ohm
=
R4 = 4.7 k-ohm
R3 = 2.2 k-ohm
Thevenins Theorem
Any circuit can
be reduced to an
equivalent circuit
consisting of a
single voltage
source and a
single resistor in
series with the
voltage source.
Power dissipation


Resistance generates heat and the
component must be able to dissipate this
heat to prevent damage.
Physical size (the surface area available
to dissipate heat) is a good indicator of
how much heat (power) a resistor can
handle

Measured in watts

Common values ¼, ½, 1, 5, 10 etc.
Power dissipation
Whenever electrical current flows
through any resistance, power is
consumed
The following formulas are used to
calculate power consumption in
electrical circuits:
P = EI or P = I2R or P = E2/R
Section 2: Review
Q.
A resistor that is Purple, Orange, and Red has
what value?
A. 7.3k with a 20% tolerance.
Q.
What is Kirchhoff’s current law?
Q.
Why is current different on each leg of a
circuit in a parallel circuit?
A. Kirchhoff’s current law states that the total current of a
parallel circuit is equal to the sum of each leg of the circuit.
A. Because with more paths for current to flow resistance
effects current differently because current takes the path of
least resistance.
Q.
Why is it important to understand Thevenins
Theorem?
A. It allows us to collapse the circuit to its basic series form.
Questions?
Section 3: Learning Objectives




Circuit analysis; finding resistance,
current, voltage values, in a series circuit,
parallel circuits and then series parallel.
Examine voltage dividers.
Determine the value of a unknown
resistor.
How capacitors are constructed, their
effects in series, and parallel circuits, and
RC time constants.
Voltage Dividers
The voltage at the junction of the
two resistors is directly
proportional to the ratio of the
two resistors. In this example
the ratio of the two resistors is
80:20.
Therefore the 80k resistor (which
is 80% of the total resistance)
drops 80% of the total voltage.
While the 20k resistor (which is
20% of the total resistance)
drops 20% of the total voltage.
(See Kirchhoff’s Voltage Law)
Therefore the 80k resistor has 80
volts across it (80% of 100
volts) and the 20k resistor has
20 volts across it.
Find the mystery voltage


What is the voltage
at the top of this
voltage divider?
The ratio of
resistances is 2:1
(200:100).
Find the mystery voltage


What is the voltage
at the top of this
voltage divider?
20V is dropped
because of the
200K resistor,
leaving 10V to be
used elsewhere.
Find the mystery Resistor Value




For this exercise there are two
resistors in series with a
battery.
The value of one resistor is
known and the other is
unknown.
The potential of the battery
and the current are known.
This exercise is useful for
finding the internal resistance
of a battery as well as other
problems.
Mystery Resistor



Now it is clear that there
are 60 mA flowing
through the 50-ohm
resistor.
Using Ohm’s law, the
voltage across the
resistor is calculated as 3
volts (0.06 amperes X 50
ohms).
Subtract 3 volts from the
battery voltage of 4.5
volts and this leaves 1.5
volt across the mystery
resistor ( Kirchhoff’s
Voltage Law
Solution

Now it is clear that
the mystery resistor
has 60 mA flowing
through it and 1.5
volts across it. Using
Ohm’s law the
resistance is
calculated at 25
ohms (1.5 V ÷ 0.06
amperes).
Variable Resistors and
Potentiometers (rheostats)



How variable resistors and
potentiometers are
constructed
Variable resistors (also called
rheostats) are constructed
with a resistive track (usually
a carbon film) that is
contacted by a wiper. There is
usually a connection at each
end of the resistive track and
another to the wiper.
If a connection is made to the
ends of the resistive track the
potentiometer looks like a
simple resistor. The wiper
makes contact anywhere
along the resistive track.
Variable Resistors and Potentiometers
Variable Resistors and Potentiometers (rheostats)
Trimpots
Potentiometer
Schematic
symbols
Potentiometer
Variable Resistor
Potentiometer as a
Variable Resistor
Capacitors in DC Circuits


Capacitance is the ability to store energy
as a volume of electricity and is measured
in farads. A one-farad capacitor would be
physically very large. Because of this,
capacitors are usually specified in
microfarads (mF) or even Pico farads (pF)
Sometimes, especially in material
published before the mid 1960s,
capacitors in the Pico farad range are
specified in micro-microfarads
(mmF). A micro-microfarad is the
same as a Pico farad
The Capacitor


Capacitance
defined
Physical
construction
Types
How construction
affects values
Power ratings

Capacitor
performance with
AC and DC
currents

Capacitance values
Numbering system

Capacitors in
circuits
Series
Parallel
Mixed
The Capacitor
The Capacitor
Defined




A device that stores
energy in electric
field.
Two conductive plates
separated by a non
conductive material.
Electrons accumulate
on one plate forcing
electrons away from
the other plate leaving
a net positive charge.
Think of a capacitor as
very small, temporary
storage battery.
The Capacitor
Physical Construction

Capacitors are
rated by:
Amount of charge
that can be held.
The voltage
handling
capabilities.
Insulating material
between plates.
The Capacitor
Capacitance Value

The unit of capacitance is the farad.
A single farad is a huge amount of
capacitance.
Most electronic devices use capacitors that
are a very tiny fraction of a farad.

Common capacitance ranges are:
 Micro
m
10-6
 Nano
n
10-9
 Pico
p
10-12
The Capacitor
Capacitance Value



Capacitor identification
depends on the
capacitor type.
Could be color bands,
dots, or numbers.
Wise to keep capacitors
organized and identified
to prevent a lot of work
trying to re-identify the
values.
The Capacitor
Ability to Hold a Charge

Ability to hold a
charge depends on:
Conductive plate
surface area.
Space between
plates.
Material between
plates.
Charging a Capacitor
The Capacitor
Behavior in DC


When connected to a DC source, the
capacitor charges and holds the
charge as long as the DC voltage is
applied.
The capacitor essentially blocks DC
current from passing through.
The Capacitor
Behavior


A capacitor blocks the passage of DC
current
A capacitor passes AC current
Capacitors in Series Circuits

Three physical
factors affect
capacitance
values.
Plate spacing
Plate surface area
Dielectric material

In series, plates
are far apart
making
capacitance less
+
Charged plates
far apart
-
C1C2
CE 
C1  C2
Capacitors in Series
Connecting capacitors in series has the
effect of decreasing the total capacitance.
This is the opposite of connecting resistors
or inductors in series.
Two capacitors of equal value connected in series
essentially doubles the distance between the
conducing plates. However, the plate area remains
the same.
The capacitors in series on the left essentially act
like this capacitor. It has the same plate area as each
of the capacitors on the left but the distance between
the plates is twice the distance of each capacitor on
the left.
To calculate the total capacitance of capacitors connected in series
use the same formula that is used for resistors in parallel.
Capacitors in Parallel Circuits



In parallel, the
surface area of the
plates add up to be
greater.
This makes the total
capacitance higher.
Add Capacitors in
Parallel as you
would resistors in
series
+
-
CE  C1  C2
Resistance With Capacitors
With a compressed air system, if there is a
restriction in the pipe leading to the storage tank,
the airflow to the tank will be impeded and the
tank will take longer to fill.
Likewise, if a resistor is placed between a
capacitor and the voltage source it will take
longer for the capacitor to charge than if the
resistor weren’t there.
Therefore, the time it takes a capacitor to charge
is a product not only of the capacitance but also
of any resistance in the circuit.
RC TIME CONSTANTS


If you multiply the
capacitance by the
resistance you will get
the number of seconds
it takes for the
capacitor to charge
63.2% of the source
voltage.
This time is called a
time constant and is
represented by the
Greek letter Tau (t).
RC TIME CONSTANTS


When discharging (assuming the capacitor
is fully charged to the source voltage), the
capacitor will discharge to 36.8% of the
source voltage during one time constant.
In this case, instead of gaining 63.2% of
the source voltage the capacitor loses
63.2% of the source voltage. (1 minus
0.632 equals 0.368). Similarly, the
capacitor will lose 63.2% of the remaining
voltage during each time constant
Calculating time constants of RC
Circuits
t = RC
If you know the time constant, the capacitance or the
resistance can be calculated by dividing the time constant
by the other parameter.
C=t/R
R=t/C
RC Charge Curve
Discharging a Capacitor
RC Discharge Curve

The discharge curve will be the inverse of the charging
curve above. The capacitor starts at the maximum voltage
then discharges toward zero volts. After one time constant
the capacitor loses 63.2% of the total voltage, leaving
36.8% of the total voltage across the capacitor.
Section 3: Review
Q. A micro-microfarad is the same as a what?
A. It is the same as a picofarad.
Q. Capacitors are said to block what?
A. Only allow a small amount of current thru when charging
or discharging, or AC current.
Q. In a parallel circuit capacitors are
calculated how?
A. Capacitors in parallel are calculated like resistors in series.
Q. Each time constant is how many percent?
A. 63.2%
Questions?
Section 4: Learning Objectives
- Learn what an inductor does in a circuit and
how it is calculated when it is placed into
series, and parallel circuit.
- How internal resistance affects a circuit.
- Types of batteries.
- Explain Metal Oxide Varistor (MOV),
Thermocouples, and Thermistor.
The Inductor


Inductance defined
Physical
construction
How construction
affects values

Inductor
performance with
AC and DC
currents
Inductors in DC Circuits
Inductance is the ability of a conductor to store
energy in a magnetic field while electric current is
passing through the conductor.
The unit of inductance is the Henry, named after the
American scientist, Joseph Henry.
Henry noticed that a spark would jump the gap
between the contacts of a switch that operated an
electromagnet.
The Inductor

There are two fundamental
principles of electromagnetics:
1. Moving electrons create a magnetic
field.
2. Moving or changing magnetic fields
cause electrons to move.

An inductor is a coil of wire through
which electrons move, and energy
is stored in the resulting magnetic
field.
The Inductor


Like capacitors,
inductors
temporarily store
energy.
Unlike capacitors:
Inductors store
energy in a
magnetic field, not
an electric field.
When the source of
electrons is
removed, the
magnetic field
collapses
immediately.
The Inductor

Inductors are
simply coils of wire.
Can be air wound
(just air in the
middle of the coil)
Can be wound
around a permeable
material (material
that concentrates
magnetic fields)
Can be wound
around a circular
form (toroid)
The Inductor



Inductance is measured in Henry(s).
A Henry is a measure of the intensity
of the magnetic field that is
produced.
Typical inductor values used in
electronics are in the range of
millihenry (1/1000 Henry) and micro
Henry (1/1,000,000 Henry)
The Inductor

The amount of
inductance is
influenced by a
number of
factors:
Number of coil
turns.
Diameter of coil.
Spacing between
turns.
Size of the wire
used.
Type of material
inside the coil.
Inductor Performance With
DC Currents



When a DC current is applied to an
inductor, the increasing magnetic field
opposes the current flow and the current
flow is at a minimum.
Finally, the magnetic field is at its
maximum and the current flows to
maintain the field.
As soon as the current source is removed,
the magnetic field begins to collapse and
creates a rush of current in the other
direction, sometimes at very high voltage.
Inductor in Series


Inductors in Series:
Values add together just as
resistors in series do.
Inductors in Parallel:
Total inductance is divided as is
the resistance in parallel.
R/L Time Constants
An RL circuit has a time constant much like
an RC circuit. In the case of RL circuits,
the time constant is calculated by dividing
the inductance by the resistance.
t = L/R
Whereas in RC circuits the formula is
t = CR
Voltage and Current with
Inductors

The time constant
curves of an RL
circuit are basically
the opposite of the
RC curves. If you look
at the curves in
Resistance with
Capacitors above and
simply label the
voltage curve as
“current” and the
current curve as
“voltage” and you will
have the curves for
an RL circuit.
Event
The switch is first
closed
The Capacitor
The Inductor
Looks like a
short circuit
Looks like an
open circuit
After one time
constant
Voltage is 63.2%
of source
voltage
Current is 63.2%
of maximum
After several time
constants
Voltage equals
the source
voltage
Current is at
maximum
The switch is
opened
Voltage reverses
across the
series
resistor
Voltage reverses
across
inductor
After one time
constant
Voltage is 36.8%
of source
voltage
Current at 36.8%
of maximum
After several time
constants
Current and
voltage are
at 0
Current and
voltage are
at 0
Other Devices in DC circuits.
Long line is +
Battery (Voltaic Cell)
Short line is -
How Batteries are Constructed
Internal Resistance
Internal resistance is a theoretical
limitation of the current sourcing
capability of a battery. Internal
resistance is calculated by dividing the
open-circuit voltage by the closed-circuit
current.
Example: if a particular battery had an open-circuit potential of
1.58 volts (typical for an alkaline battery) and a closed-circuit
current of 1 ampere, the internal resistance would be 1.58 ohms
EXERCISE
Find the internal resistance:
A battery rated at 1.58 Volts delivers
138ma through a load of 8 ohms.
What is the internal resistance???
Solution
Using Ohm’s law:
Total resistance is calculated as 11.5 ohms (using
the source voltage of 1.58 volts and the current
of 138 milliamperes, i.e., (1.58V / 0.138A=
11.449 ohms).
Subtract the load resistance (8 ohms) from the
total resistance to find the unknown internal
resistance of :
3.5 ohms (11.449 - 8 = 3.449).
Applications and Safety




Battery terminals should never be
shorted for long periods
Never mix old and new batteries
Some batteries contain powerful
acids
Never recharge non rechargeable
batteries
Types of Batteries

Primary (Non rechargeable)
Carbon Zinc
Alkaline
Lithium
Mercury Oxide
Types of Batteries Cont’d

Secondary (Rechargeable)
Nickel Cadmium
Nickel-metal hydride
Lithium ion
Rechargeable Alkaline
Lead Acid
Fuses



Melt open when a
certain current is
exceeded
Will “blow” when the
current reaches 1.5
times the labeled
current rating
Installed in SERIES
with the load
Fuse schematic symbol
METAL OXIDE VARISTOR (MOV)
Used for over voltage protection or “surge”
protection.
Connected in Parallel with the load.
Once burned open, they no longer do their
job and need to be replaced.
Used in Surge protectors.
Thermocouple
Thermocouples are very simple
and durable temperature
sensors. They are comprised
of two different materials
joined at one end and
separated at the other.
The separated ends are
considered the output, and
they generate voltage which
is proportional to the heat
they are measuring or
monitoring.
Thermister


A thermistor changes resistance with temperature, like a
normal resistor, except more pronounced. Thermistors, like
thermocouples are used to measure temperature, but in
less hostile environments.
Thermisters come in two types, those with positive
temperature coefficients and those with negative
coefficients. The resistance of a thermistor with a negative
temperature coefficient will go down as the temperature
rises. This is the opposite of most electronic devices.
Thermistor schematic symbols
Section 4: Review
Q. How does a\the number of turns of wire
affect an inductor?
A. Inductance increases with the number of turns.
Q. How does a R/L time constant differ from
an R/C time constant?
A. t=RC; t=L/R
Q. Metal Oxide Varistors protect what?
A. Used for over voltage for surge protectors.
Q. Thermocouple generate voltage how?
A. Using 2 dissimilar metals bonded together creates
milli-volts.
Questions?
Section 5: Learning Objectives
-
-
-
-
Alternating Current, how it differs from
DC.
Be familiar with Alternators, Oscillators
and four parameters of a Sine Wave.
Understand the difference between RMS
voltage, Peak Voltage, and Peak to peak
voltage.
Calculate capacitive reactance, inductive
reactance, and impedance in series and
parallel circuits.
Alternating Current


Alternating current simply means
that the polarity of the voltage
source alternates back and forth.
Alternating current can be
generated with either an
alternator (and alternating
generator) or an oscillator
Show- AC - Verses -DC
Alternators

An alternator
generates
electricity by
rotating coils of
wire in a magnetic
field. As the coils
pass one way,
current flows in one
direction. As the
coils pass the other
way (on the second
half of the rotation)
current flows in the
other direction.
In an alternator a loop of wire
rotates through a magnetic field
and generates a sine wave on
the oscilloscope.
How an oscillator works






Energy needs to move back and forth from one form to another for an
oscillator to work. You can make a very simple oscillator by connecting
a capacitor and an inductor together. If you've read How Capacitors
Work and How Inductors Work, you know that both capacitors and
inductors store energy. A capacitor stores energy in the form of an
electrostatic field, while an inductor uses a magnetic field. Imagine
the following circuit:
If you charge up the capacitor with a battery and then insert the
inductor into the circuit, here's what will happen:
The capacitor will start to discharge through the inductor. As it
does, the inductor will create a magnetic field.
Once the capacitor discharges, the inductor will try to keep the
current in the circuit moving, so it will charge up the other
plate of the capacitor.
Once the inductor's field collapses, the capacitor has been
recharged (but with the opposite polarity), so it discharges
again through the inductor.
This oscillation will continue until the circuit runs out of energy due to
resistance in the wire. It will oscillate at a frequency that depends on
the size of the inductor and the capacitor.
Oscillators


An oscillator is a circuit that
produces an output that varies
periodically. They are used as
clocks for timing circuits, to
drive digital circuits or as
essential components of radio
circuits.
The following are
characteristics of oscillators
 Positive feedback
 An oscillator will often have a
tuned circuit in the feedback
loop.
 Gain of 1
A Colpitts oscillator
Pierce Oscillator
Armstrong Tuned-Gate Oscillator
Hartley Oscillator
The Sine Wave
The output of an
alternator is a sine
wave. A sine wave is
the most pure
waveform possible. In
fact, any repetitive
wave is made up of
one or more sine
waves.
The sine wave is
closely related to a
circle and parts of the
wave are measured in
degrees as a circle is .
Four parameters of a Sine
Wave




Amplitude
Peak Voltage
RMS voltage
Phase Angle
Phase angle
A sine wave is
closely related
to a circle. For
phase
measurements
the wave is
divided into 360
degrees, just as
a circle is.
One cycle of a sine wave is
measured in 360 degrees.
Frequency

Frequency is the
number of times
the wave completes
one cycle in one
second. It is
measured in Hertz
(Hz) where 1Hz
equals one cycle
per second, 20 Hz
equals 20 cycles
per second, etc
The 60Hz sine wave on the left takes
twice the time to complete one cycle as
the 120Hz sine wave on the right (16.6
milliseconds compared to 8.33
milliseconds).
Period


The period of a wave
is the time it takes
to complete one
cycle.
Mathematically it is
the reciprocal of the
frequency. For
example, a 60Hz
wave has a period of
16.6 ms (1 / 60 =
0.0166).
Other Waves

If a circuit does not have the
necessary frequency response
(bandwidth) to pass all components
of a wave (harmonics), the wave will
be distorted.
Square Wave
High-pass filter
Distortion due to insufficient
low frequency response.
Measurements

AC Voltmeter – Reads RMS Voltage
which is 70.7% of peak voltage. Only
accurate for measuring sine waves.
Oscilloscope


An oscilloscope is an
analog voltmeter that
measures voltage over
time
Voltage is represented by
vertical movement of the
spot along the Y-axis. As
the spot moves upward it
represents more positive
voltage. As it moves
down it represents more
negative voltage.
The face of an oscilloscope showing a sine wave.
The spot moves along the horizontal X-axis over a
given time. Vertical movement along the Y-axis
represents volts. This shows the repeated sinusoidal
change in voltage over time of a sine wave.
Dual Trace O-Scope

A dual trace
oscilloscope has
two vertical (Y
axis) inputs.
Although the
spots move
horizontally in
unison, they
move vertically
independently.
A dual trace oscilloscope has two Y-axis
inputs that measure voltage
independently.
O-Scope X10 Probe

Any test instrument takes some
current from the circuit. This can be
enough current to cause a voltage
drop and change the way the circuit
is operating…..
Because of this, a X10 probe is used.
Circuits


A circuit is a path for current to flow
Three basic kinds of circuits
Open – the path is broken and
interrupts current flow
Closed – the path is complete and
current flows were it is intended
Short – an unintended low resistance
path that divers current
Resistors in AC Circuits
Resistors in AC Circuits are insensitive
to frequency or phase.
The Capacitor
Behavior in AC




When AC voltage is applied, during
one half of the cycle the capacitor
accepts a charge in one direction.
During the next half of the cycle, the
capacitor is discharged then
recharged in the reverse direction.
During the next half cycle the
pattern reverses.
It acts as if AC current passes
through a capacitor
Capacitors in AC Circuits
Alternating current simply repeats
the charge discharge cycle of a
capacitor at a given frequency. At
higher frequencies, the capacitor
passes more current than at lower
frequencies.
Capacitive Reactance


The property of a capacitor where it
passes more current at higher frequencies
is called capacitive reactance. It is
measured in ohms, like resistance, but is
different at different frequencies.
For example, if a capacitor has a
reactance of 10 ohms at 100 Hz it will
have a reactance of 5 ohms at 200 Hz.
Calculating Capacitive
Reactance


Since the reactance of a capacitor is different at different
frequencies you need to be able to calculate the reactance based
on the size of the capacitor.
The formula to calculate capacitive reactance is:
Where:
XC
=
capacitive reactance in ohms
2p
=
a mathematical constant of 6.28

=
frequency of the AC source voltage in hertz
C
=
capacitance in farads
Capacitive Reactance



In the following circuit the capacitive reactance is calculated
as below:
The source voltage has a frequency of 60 hertz and the
capacitance is 66 microfarads. Plugging these numbers into
the above formula we get:
This gives a capacitive reactance (XC) of 40.2 ohms.
Voltage and Current in a Capacitive
AC Circuit



Voltage and
Current in a
Capacitive AC
Circuit
While the voltage is
low, the current is
high and vice-versa.
In this case, the
current is said to lead
the voltage (high
current followed by
high voltage).
Above: Voltage and current across a capacitor
when a sine wave is applied.
Below: Voltage and current of a capacitor during
charge and discharge cycles
The Inductor

Because the
magnetic field
surrounding an
inductor can cut
across another
inductor in close
proximity, the
changing
magnetic field in
one can cause
current to flow in
the other … the
basis of
transformers
Inductors in AC Circuits

Inductive Reactance



Inductors block current flow at the
start of the “charge and discharge”
cycles of a sine wave. The faster the
cycles, the less current an inductor will
pass.
This opposition to high frequencies is
called inductive reactance
Higher frequencies = More inductive
reactance
Calculating Inductive Reactance


The formula to
calculate inductive
reactance is:
XL = 2πfL
XL
= inductive
ohms
reactance
in
2p
= a mathematical constant of
6.28

= frequency of the AC source
voltage in hertz
L
= inductance in henrys
Inductive-Capacitive Circuits



A circuit is either inductive or capacitive
depending on whether XL or XC is higher.
The total reactance is the difference
between the inductive reactance and the
capacitive reactance:
X = Abs (XC – XL)
X
=Total reactance
Abs
=Absolute value, meaning if the result is negative remove
the minus sign
XC
=Capacitive reactance in ohms
XL
=Inductive reactance in ohms
Impedance Series Circuits


Impedance is the combination of all the resistance and reactance
in a circuit. It is represented by the letter Z and is calculated with
the following formula.
If this formula looks familiar, it is the same formula used to
calculate the length of the side of a right triangle knowing the
lengths of the other two sides (the Pythagorean theorem).
For Example:

If you have a total
reactance of 25
ohms (say, 75 ohms
of inductive
reactance and 50
ohms of capacitive
reactance) and 75
ohms of resistance,
you will have an
impedance of 79.1
ohms. Since the
reactance's have
cancelled to only 25
ohms, and there is
75 ohms of
resistance, the
circuit is resistive.
Impedance formula Parallel

Parallel Impedance formula is the
inverse of Series formula.
Resonant Circuits



Remember that as frequency increases inductive
reactance increases. Likewise, as frequency
increases capacitive reactance decreases.
This means that, with any circuit having both
inductance and capacitance, there must be a
frequency where the inductive reactance and
capacitive reactance are the same.
The frequency where inductive reactance
and capacitive reactance are equal is called
the resonant frequency.
Resonants
Resonant Frequency Formula:
In the following circuit the resonant
frequency would be calculated by plugging
the values for the inductor and capacitor
into the above formula:
If either inductance or capacitance increases, the resonant
frequency decreases and vice-versa.
Series Resonance




In the example series resonant circuit
the inductor and capacitor are
connected in series.
As shown here to find the total
reactance, the capacitive reactance is
subtracted from the inductive
reactance.
Since the inductive reactance and the
capacitive reactance are equal at the
resonant frequency, the total
reactance will be zero.
If there is resistance in the circuit,
the total impedance will be the value
of the resistance. Therefore, a series
resonant circuit will have its lowest
impedance at the resonant frequency.
Parallel Resonance


In a parallel resonant
circuit, the inductor will
have lower reactance at
low frequencies and the
capacitor will have lower
reactance at high
frequencies.
Therefore, a parallel
resonant circuit will
have its highest
impedance at the
resonant frequency.
Review 5: Questions
Q. How does an Oscillator work?
A. As the Cap starts to charge the inductor starts to create a
magnetic field. When the capacitor discharges the inductor will
try to keep the current in the circuit moving so it will charge up
the other plate. Once the inductors field collapse the capacitor
has been recharged so it discharges through the inductor.
Q. What is Amplitude, Peak voltage, Peak to
Peak, and RMS?
A. Amplitude represents how large the wave is. Peak voltage is the
maximum voltage in either direction. Peak to Peak is Maximum
(+) (-). RMS is converted to DC or 70.7%.
Q.
Why is a X10 probe used by an O-Scope?
A. To minimize circuit loading. Always multiply readings by 10.
Questions?
Section 6: Learning Objectives
- Explains some uses of a filter
system and why a filter is needed in
electronics applications.
- Know the differences between a
high pass filter and a low pass filter.
- Understand the differences between
the types of transformers.
- Be familiar with the efficiency
problems with transformer.
Filters


Filters are used where a range of
frequencies are desired and another
range is not.
A typical use of a filter circuit is a
crossover network in a speaker
system. In this case it is desirable to
direct frequencies above a certain
point to the tweeter and those lower
than that point to the woofer
RC Filters

Low Pass
In a circuit made of a single resistor
and a single capacitor, there is a
frequency where the capacitive
reactance and the resistance will be
equal. This frequency is called the cutoff frequency (fCO).
Looking at the following circuit, at
frequencies below the cut-off
frequency more voltage will be
developed across the capacitor than
the resistor; at frequencies above the
cut-off frequency more voltage will be
developed across the resistor than the
capacitor. Another definition of the cutoff frequency is the half-power point.
This is because the power output of
the filter is 50% of the maximum at
the cut-off frequency.
RC L low pass Filter

An RC filter is
typically
illustrated with
the following
configuration.
Since the circuit
takes the shape
of the letter “L”,
it is called an “L”
filter
An RC “L”
low-pass filter.
RC Filter Cont’d



In an RC filter circuit, the
input is placed across the
two components in series
and the output is taken
across one of the
components.
If the output is taken
across the resistor the
filter becomes a high-pass
filter; if the output is take
across the capacitor the
filter is a low pass filter.
The cut-off frequency of an
RC filter is calculated with
the following formula:
co =
Cut-off frequency
2p = Mathematical
constant of 6.28
R
=
C
=
Resistance in ohms
Capacitance in ohms
High Pass RC Filters


When the output is taken
across the resistor, you
have a high Pass filter.
Another way to look at the
high pass filter is that the
higher frequencies are
passed by the capacitor
and the lower frequencies
are blocked by the
capacitor.
An RC “L”
high-pass filter
LC Filters

LC filters have the advantage of not wasting energy as power
dissipated in the resistor.

In an LC filter you actually have a resonant circuit. Therefore,
the cut-off frequency will be the resonant frequency.

At frequency above the resonant frequency the inductive
reactance is greater than the capacitive reactance.

Therefore the voltage across the inductor is higher than the
voltage across the capacitor.

At frequencies below the resonant frequency the capacitive
reactance is greater than the inductive reactance. Therefore the
voltage across the capacitor is higher than the voltage across the
inductor.
High Pass LC Filters

If the output is
taken across the
inductor of an LC
filter you have a
high-pass filter.
Another way to
look at it is that
the capacitor
blocks lower
frequencies and
the inductor
passes what’s left
to ground
Low Pass LC Filters

If the output is
taken across the
capacitor of an LC
filter you have a
low-pass filter.
Another way to look
at it is that the
inductor blocks
higher frequencies
and the capacitor
passes what’s left to
ground.
L Filters and T Filters

“T” filters can have any
combination of
components and be
either low-pass or highpass filters .
Pi Filters

Like the “T” filter, the
Pi filter is usually
illustrated with the
components laid out
in the shape of the
Greek letter Pi. Like
the “T” filter can use
any combination of
components and be
either low-pass or
high-pass.
A low-pass
CLC Pi filter
A low-pass
CRC Pi filter
Transformers


Joseph Henry and Michael
Faraday independently
discovered that a changing
current in an inductor would
induce a current in a nearby
inductor. Credit for this property
of mutual inductance has been
given to Faraday.
Modern transformers are
constructed by winding two coils
of wire, either next to each other
or one on top of the other, on a
core made of either soft iron
(actually, usually steel) or
ferrite. The soft iron
concentrates (“controls and
directs”) the magnetic lines
of flux in the transformer
How Transformers Work…

When an AC current is
passed through one of the
inductors making up a
transformer, the
oscillating magnetic flux
crossing the other
inductor induces AC
current in that inductor.
The inductor that has
current passed through it
is called the primary
inductor; the inductor that
has the induced current is
called the secondary
inductor. In this case the
transformer is called a
step-down transformer.
Output Voltage of a Transformer
The output
voltage of a
transformer
is determined
by the ratio
of coils
(turns) of
wire between
the two
inductors.
Types of Transformers






Step up/Step Down
Isolation
Impedance Matching
Tapped
AutoTransformer
Tesla Coil
Step Up- Step Down
Transformer



In a step-up transformer the secondary voltage is higher
than the primary voltage
In a step-down transformer the secondary voltage is lower
than the primary voltage.
A step-up or step-down transformer can be reversed to
perform the opposite function. However a transformer is
usually optimized for either step-up or step-down
operation.
What would be the ratio of this
Transformer?
What would be the Ratio of this
Transformer?
Isolation Transformer




An isolation transformer has the same voltage on the
secondary as on the primary.
The primary and secondary may be optimized for the
circuits they are intended to couple but otherwise the
primary and secondary are identical.
The main purpose of an isolation transformer is to block DC
currents.
They may also be used to isolate equipment from the
receptacle power. These isolation transformers may have a
variable output but don’t mistake a “variac” (explained) for
an isolation transformer.
Impedance Matching

A matching transformer used to
match the impedance between two
circuits. This maximizes power
transfer.
Tapped Transformer


Transformers often have taps in the
secondary to make more than one
voltage available.
These may be center-tapped to give
two equal voltages or may have
various taps to give various voltages.
Autotransformer


An autotransformer is a
single coil that is tapped in
such a way that the primary
and secondary are different
parts of the coil, although
one may completely overlap
the other.
A Variac is a brand name for
an autotransformer with
variable output.

The ignition coil of a car is
usually an autotransformer.

Do not confuse with the
Isolation Transformer
Tesla Coil

A Tesla coil, invented by Nicola Tesla,
is a type of autotransformer that is
driven by a resonant oscillator. Very
high voltages and currents can be
achieved with a Tesla coil.
Efficiency

Transformers are extremely efficient.
However there are some losses.
Core losses
Hysteresis
Eddy Currents
Copper Losses
Core losses

Core losses are caused by power
consumed by the core of the
transformer
Hysteresis

Hysteresis is the resistance of a
material to change the polarity of its
magnetism. With each oscillation of
the transformer current the polarity
of the magnetic domains in the core
are reversed. This consumes power
and produces heat.
Eddy currents



The transformer core is made of soft iron, a
conductor.
Since this core is within the oscillating magnetic
field, electric current will be induced in it. This
current does nothing useful and produces heat.
Transformer cores are usually made of laminated
plates coated with enamel. The enamel insulates
the layers of the core from each other, reducing
the eddy currents.
Copper losses


Copper losses are mainly cause by the resistance
of the wire that makes up the transformer.
Copper losses can be reduced by increasing the
diameter of the wire. If a transformer needs to
transfer a high current, larger wire must be used
to reduce copper losses. Consequently a larger
iron core must also be used.

Copper losses determine the maximum output
current of a transformer.

When the current rating of a transformer is
exceeded, copper losses cause a drop in voltage.
Decibels


The term “decibel” means
1/10 of a bel, named after
Alexander Bell of telephone
fame.
The bel is used to express
large power ratios with
smaller numbers.
db
=
Power ratio in decibels




One bel is a ratio of 10:1,
two bels is a ratio of 100:1,
3 bels is a ratio of 1,000:1,
etc.
Since one decibel is 1/10 of a
bel 10 decibels equals one bel
or a ratio of 10:1. The
formula to calculate decibels
is:
Log
=
Base-10 logarithm
P1
=
P2
=
Reference power level
Compared power level
Decibels as Voltage ratios:

Decibels are only
intended to express
power ratios. However,
since power and voltage
are directly proportional
to each other, decibels
can also be used to
express voltage ratios.
The formula to calculate
decibels using a voltage
ratios is:
Decibels



The power ratio of 2:1 or
three decibels (3db)
appears frequently in
nature. For example, the
human ear can normally
only detect differences in
sound level of 3db
(someone with
inflammation of the inner
ear may be able to detect
a 1db difference).
Bandwidth is specified as
the range of frequencies
where the output of a
circuit is less than 3db
below the peak output.
Here is a table of decibels
and their respective ratios.
Power or
Voltage
Ratio
Decibels
Voltage
Power
1.26:1
2
1
2:1
6
3
10:1
20
10
100:1
40
20
1,000:1
60
30
etc.
etc.
etc.
Review 6: Questions
Q. What is the main purpose to use a high pass
filter?
A. To allow the high frequency to drive something like a
tweeter.
Q. What is hysteresis?
A. Hysteresis is the resistance of a material to change the
polarity of its magnetism.
Q. An Isolation Transformer’s main purpose is to
do what?
A. The main purpose of an isolation transformer is to block
DC currents.
Q. A Decibles ratio of 2:1 in voltage would
be what loss?
A. 6 Volts.
Questions?
Section 7; Learning Objectives




Understand how a P/N junction is able to
operate.
Know the types of Diodes and their
purposes.
Be familiar with rectification using a half
wave rectifier and a full wave rectifier.
Recognize the components of a transistor
and the basic principles of operations for
the transistor.
Solid State Electronics
Silicon Atom



A silicon atom has four
electrons in its outermost shell
(the valence shell, where all
chemical and electrical action
takes place).
When silicon forms a crystal,
each of the four valence
electrons will bond with an
electron from an adjacent
silicon atom.
These electrons are bound
tightly in the crystal lattice and
are hard to move, making a
silicon crystal an insulator.
Silicon Crystal
Lattice
Arsenic Atom

An arsenic atom has five electrons in its
valence shell If a small number arsenic
atoms are introduced into a silicon crystal,
four of the electrons will bind with
electrons in adjacent silicon atoms and the
arsenic will fit into the crystal lattice.
However, the fifth electron has no
electrons to bind with. These “donor”
electrons want to remain with the arsenic
atoms because they are attracted to a
corresponding proton in the atom.
However, not having an electron to bond
with in the crystal lattice, this extra
electron acts much like the electrons in
metals. The arsenic atoms in the silicon
N-Type Silicon
crystal can easily exchange these loose
Notice that each arsenic atom has an extra
electrons. Since the donor electrons are
easily moved through the crystal, it will
electron that doesn’t fit the lattice.
readily conduct electrical current. A silicon
crystal that is “doped” with donor atoms is
called N-type silicon.
The gallium atom

A gallium atom has three electrons
in its valence shell. If a small
number of gallium introduced into
a silicon crystal the three electrons
will bind with electrons from
adjacent silicon atoms but there
will be a “hole” left with no atom.
Any electrons that happen by will
easily fall into the holes left by the
gallium atoms but, since there is
no corresponding proton in the
gallium atom to hold them, they
are easily pushed out of the holes.
Since electrons can be easily
moved through the crystal,
hopping from hole to hole, the
crystal will readily conduct
electrical current. A silicon crystal
that is doped with atoms that
leave holes in the crystal structure
is called P-type silicon.
P-Type Silicon
Notice that each gallium atom is short of
one electron, leaving a hole in the lattice.
Properties of Silicon in Solid state
devices
Silicon Crystal Lattice
N-Type Silicon
Notice that each arsenic atom has
an extra electron that doesn’t fit the
lattice.
P-Type Silicon
Notice that each gallium atom is
short of one electron, leaving a
hole in the lattice.
P/N junction

If P-type silicon and N-type
silicon are brought into
contact, electrons in the Ntype silicon will be strongly
attracted to the holes in the
P-type silicon near the
junction. The attraction of the
holes in the P-type silicon is
stronger than the attraction
of the protons in the donor
atoms. However, donor
electrons must remain near
their atoms because they are
attracted to a corresponding
proton in the donor atom.
The result is that, near the
junction of the P-type and Ntype materials, the donor
electrons move to nearby
holes in the P-type material
and the crystal lattice
becomes complete. The
region is depleted of donor
electrons and holes and will
not readily conduct electricity
A P-N Junction
Look near the middle of the lattice. To
the left the silicon is doped with arsenic.
To the right the silicon is doped with
gallium. The holes created by the
gallium atoms attract the electrons
donated by the arsenic atoms (the
darkened electrons).
Analyzing Charge Carriers
(Electrons and Holes)


To avoid confusion we must now adjust how we view the
structure of a semiconductor crystal. We need to start
looking at N-type silicon as material with free negative
charge carriers (electrons) and P-type silicon as a material
with free positive charge carriers (holes).
Now, when we look at a P-N junction we have a
different picture. Think of it like this, if you dig a hole
in the ground, what do you get? Not only a hole in
the ground but a pile of dirt that used to be in the
hole. If you put the dirt back in the hole, neither the
hole nor the pile of dirt exists anymore. In the
depletion region, where the electrons from the Ntype side have filled the holes in the P-type side,
neither the free electrons nor the holes exist, as
charge carriers, anymore
Another View of a P-N Junction

Electrons in the Ntype silicon near the
junction have
migrated to fill the
holes in the P-type
silicon near the
junction. Charge
carriers no longer
exist near the
junction. The
depletion region is
the region devoid of
charge carriers.
Reversed Biased P/N Junction

When a positive potential is applied
to the N-type side and a negative
potential is applied to the P-type side
the junction is said to be reverse
biased. The free electrons in the Ntype silicon are pulled out of the
crystal by the positive voltage. The
negative voltage applied to the Ptype side floods the P-type silicon
with electrons that fill the holes in
the crystal lattice. Since filling the
holes with electrons makes them
cease to exist as charge carriers it
appears that the holes have been
pulled out of the P-type silicon by
the negative potential. This leaves
the entire crystal devoid of charge
carriers. Under normal voltage levels
electrical current will not flow
through the crystal.
Forward-biased P-N Junction




When a positive potential is applied to
the P-type side and a negative potential
is applied to the N-type side, the junction
is said to be forward-biased.
Free electrons are pushed toward the
junction by the negative potential. The
positive potential applied to the P-type
side pulls electrons out of the holes so it
appears that holes are pushed toward the
junction.
If enough voltage is applied, the
electrons and holes are forced into the
depletion region. With the crystal now
filled with charge carriers it conducts
electrical current.
A forward biased P/N junction will take a
certain amount of voltage to force the
electrons to start flowing.
The Diode


A diode is an electrical device allowing current to
move through it in one direction with far greater
ease than in the other.
The most common type of diode in modern circuit
design is the semiconductor diode, although
other diode technologies exist. Semiconductor
diodes are symbolized in schematic diagrams as
such:
Diodes

When placed in a simple batterylamp circuit, the diode will either
allow or prevent current through the
lamp, depending on the polarity of
the applied voltage:
Diodes


When the polarity of the battery is such that electrons are
allowed to flow through the diode, the diode is said to be
forward-biased.
Conversely, when the battery is "backward" and the diode
blocks current, the diode is said to be reverse-biased. A
diode may be thought of as a kind of switch: "closed" when
forward-biased and "open" when reverse-biased.
DIODES

Diode behavior is comparable to the
behavior of a hydraulic device called
a check valve. A check valve allows
fluid flow through it in one direction
only:
DIODES
Diodes
DIODES



For silicon diodes, the typical forward
voltage is 0.7 volts, nominal.
For germanium diodes, the forward
voltage is only 0.3 volts.
The chemical constituency of the P-N
junction comprising the diode accounts for
its nominal forward voltage figure, which
is why silicon and germanium diodes have
such different forward voltages.
Diodes
Diodes
General
Purpose
Zener
Light Emitting
(LED)
The Diode
The semi-conductor phenomena



Atoms in a metal allow a “sea” of
electrons that are relatively free to
move about.
Semiconducting materials like Silicon
and Germanium have fewer free
electrons.
Impurities added to semiconductor
material can either add free
electrons or create an absence of
free electrons (holes).
The Diode
The semi-conductor phenomena

Consider the bar of silicon at the right.
 One side of the bar is doped with negative
material (excess electrons). The cathode.
 The other side is doped with positive material
(excess holes). The anode
 In between is a no man’s land called the P-N
Junction.
The Diode
The semi-conductor phenomena



Consider now applying a negative
voltage to the anode and positive
voltage to the cathode.
The electrons are attracted away
from the junction.
This diode is reverse biased meaning
no current will flow.
The Diode
The semi-conductor phenomena



Consider now applying a positive voltage
to the anode and a negative voltage to the
cathode.
The electrons are forced to the junction.
This diode is forward biased meaning
current will flow.
The Diode
with AC Current

If AC is applied to a diode:
During one half of the cycle the diode is
forward biased and current flows.
During the other half of the cycle, the diode is
reversed biased and current stops.


This is the process of rectification,
allowing current to flow in only one
direction.
This is used to convert AC into pulsating
DC.
The Diode
with AC Current
Output Pulsed DC Voltage
Diode
conducts
Diode off
Input AC
Voltage
The Light Emitting Diode



In normal diodes, when electrons combine
with holes current flows and heat is
produced.
With some materials, when electrons
combine with holes, photons of light are
emitted, this forms an LED.
LEDs are generally used as indicators
though they have the same properties as
a regular diode.
Rectifier

This converts the AC from the receptacle
to a pulsing DC. This is done by removing
or inverting half of the AC signal. Because
of the pulsing nature of the DC produced
by the rectifier, the final output will always
have some ripple. The type of rectifier
determines the frequency of this ripple.
For example, with a 60 Hz input, a halfwave rectifier will have a ripple frequency
of 60 Hz where a full-wave rectifier will
have a ripple frequency of 120 Hz.
Rectifier (Cont’d)
Unregulated power supply
with half-wave rectifier
Unregulated power supply
with full-wave bridge
rectifier
Half-wave rectified
sine wave
Full-wave rectified sine
wave
Typical ripple after filtering.
Ripple frequency equals the
sine wave frequency
Typical ripple after filtering.
Ripple frequency equals two
times the sine wave frequency.
Full Wave Rectification
First Half of AC Cycle (+)
Second Half of AC Cycle (-)
FWBR in action
AC in – Pulsating DC out
Zener Diode

A Zener diode is
designed through
appropriate doping
so that it conducts
at a predetermined
reverse voltage.
The diode begins to
conduct and then
maintains that
predetermined
voltage

The over-voltage
and associated
current must be
dissipated by the
diode as heat
9V
4.7V
Thyristors




SCR's are the most prevalent member of the thyristor four layer
diode family.
A positive pulse applied to the gate of an SCR triggers it into
conduction. Conduction continues even if the gate pulse is
removed. Conduction only ceases when the anode to cathode
voltage drops to zero.
SCR's are most often used with an AC supply (or pulsating DC)
because of the continuous conduction.
SCR's switch megawatts of power, up to 5600 A and 10,000 V.
The Transistor
(Electronic Valves)


How they work, an inside
look
Basic types
NPN
PNP

The basic transistor
circuits
Switch
Amplifier
Transistor
NPN
PNP
FET
The Transistor
collector
base
emitter
NPN and PNP
The Transistor
The base-emitter current controls the collector-base current
The Transistor
Applying positive Voltage to the Base
The Transistor



There are two basic types
of transistors depending of
the arrangement of the
material.
PNP
NPN
An easy phrase to help
remember the appropriate
symbol is to look at the
arrow.
PNP – pointing in
proudly.
NPN – not pointing in.
The only operational
difference is the source
polarity.
PNP
NPN
Bipolar Transistors


A bi-polar transistor is
made of three layers of
silicon in a P-N-P or NP-N arrangement
Since the current that
flows into the collector
of a bi-polar transistor
is a ratio of the current
flowing into the base,
bi-polar transistors are
said to amplify current
A small current from the base to the emitter causes a
large current from the collector to the emitter (Note:
conventional current is shown.).
A PNP transistor works like an NPN transistor except
the polarities are reversed.
Bipolar Transistors

The following illustrations show the
polarity and schematic symbols for
bi-polar transistors..
MOSFET Transistors


Field-Effect Transistors are
constructed in several ways using
metal-oxide-semiconductor
technology. The leads on a FET are
labeled Drain, Source and Gate.
Because the current through an FET
(MOSFET) is a ratio of the gate
voltage, FETs are said to amplify
voltage.
Integrated Circuits



The first integrated circuits were simply a
few transistor manufactured on a single
chip of silicon. Today, integrated circuits
are made-up of millions of transistors
along with other components and
interconnections.
We are concerned here mainly with digital
integrated circuits. There are several
families of digital integrated circuits.
The ones that will be covered here are TTL
and CMOS.
TTL Circuits


TTL (Transistor-Transistor Logic) integrated
circuits are made using bi-polar
transistors. The gates in TTL circuits are
often characterized by multiple emitters
on a single transistor. TTL circuits have the
advantage of speed at a sacrifice of power
efficiency.
TTL circuits always operate from 5-volt
power supplies (typically specified as from
4.5 or 4.75 volts to 5.25 or 5.5 volts).
TTL Nand Gate
CMOS





CMOS (Complementary Metal OxideSemiconductor) integrated circuits
are made using MOS field-effect
transistors.
Each gate is made from a
complementary pair of transistors
(I.e. one p-channel and one nchannel transistor).
CMOS circuits have the advantage of
very low power consumption but are
much slower than TTL circuits.
CMOS circuits are also very
sensitive to electrostatic
discharge.
CMOS circuits typically operate
from power supplies ranging
from 3 to 12 volts.
Pinouts


The pinout of an IC is read counterclockwise looking from the top.
Pin one is indicated by a tab on TO-3
packages and by a dot or notch on
DIP packages.
Dip
TO-5
Troubleshooting IC Circuits



Troubleshooting techniques for ICs are
similar to other circuits.
It is important to have the internal
schematics available or to be familiar with
how the circuit should behave.
Since all of the components are on a
single silicon chip, failure is often indicated
by open an or short-circuit condition.
Review 7: Questions
Q. What is an arsenic atom and its purpose?
A. It is the N-type material and it contains an extra atom to
fill the holes to allow voltage to flow thru once it is
properly forwarded biased.
Q. Does a Zener Dioad conduct in forward or
reverse bias?
A. Reverse bias.
Q. An Isolation Transformer’s main purpose is to
do what?
A. The main purpose of an isolation transformer is to block
DC currents.
Q. A Decibles ratio of 2:1 in voltage would
be what loss?
A. 6 Volts.
Amplifiers

Bi-polar Transistor Amplifiers

There are three basic amplifier configurations for bi-polar
amplifiers.
 Common Collector
 Common Emitter
 Common Base

These are named for the connection that is used for the common
connection in the circuit.

It is usually easier to recognize a configuration by the location of
the output.

Each configuration has characteristic input and output impedances
and AC voltage gain.
Common Collector
(Emitter follower)
The Common Collector configuration can be
recognized by the output being on the emitter:

High input impedance

Low output impedance

Output not inverted

Voltage gain (AV) of 1
Common Emitter
The Common Emitter configuration can be
recognized by the output being on the
collector

Low input impedance
High output impedance
(equal to collector
resistor)


Output inverted

High voltage gain
Common Base
The Common Base amplifier can be
recognized by the base being tied to the
circuit ground.

low input impedance

high output impedance

high voltage gain

current gain <1
Operational Amplifiers



An operational amplifier is a very
high gain differential amplifier with
very high input impedance and a
very low output impedance.
The two inputs of an operational
amplifier are labeled with plus and
minus symbols.
The plus input is called the noninverting input and the minus input
is called the inverting input.
OP Amps



Differential amplifier - amplifies
difference between two signals.
Can amplify very small voltage
signals to a useful level.
Op Amps can require one power
supply (single supply) or a
positive and a negative power
supply (dual supply)
An operational amplifier follows a
few simple rules:



If the non-inverting input is more positive than the
inverting input, the output voltage will go more positive
until one of two conditions are met. Either the two inputs
are equal or the output cannot go more positive (usually
about 0.5 volts below the positive supply voltage.)
If the inverting input is more positive than the noninverting input, the output voltage will go more negative
until one of two conditions are met. Either the two inputs
are equal or the output cannot go more negative (usually
about 0.5 volts above the negative supply voltage).
The output voltage will remain stable as long as the
two input voltages are equal
Op Amp Applications:



Comparator
Since there is no feedback there is
no effect on the inputs based on the
output voltage. Therefore, as long
as the inverting input is the least-bit
more positive that the non-inverting
input (with the exception of
unavoidable hystersis), the output
voltage will go all the way to the
negative supply voltage and remain
there.
Likewise, as long as the noninverting input is the least-bit more
positive than the inverting input,
the output voltage will go all the
way to the positive supply voltage
and remain there.
Op Amp Applications:



Voltage Follower
The output is fed back, 100%,
to the inverting input.
Following the foregoing rules,
the output voltage will be
automatically adjusted until
the two inputs are equal.
With the 100% negative
feedback, the two inputs can
only be equal when the output
is equal to the non-inverting
input. Therefore, the output
voltage will always be equal to
the input voltage (at the noninverting input). This circuit is
useful to couple a circuit with
high output impedance to a
circuit with low input
impedance
Op Amp Applications:



Non-inverting Amplifier
The output is fed back to the
inverting input through a voltage
divider. Following the voltage
divider rules, if the feedback
resistors are equal, the voltage at
the inverting input will be 50% of
the output voltage.
Therefore, for the inputs to be
equal, the output voltage must be
twice the input voltage (at the
non-inverting input). The gain can
be adjusted by changing the ratio
of the feedback resistor values.
Op Amp Applications:




Inverting Amplifier
The non-inverting input is at the
circuit ground. Therefore, the output
voltage will be adjusted
automatically to keep the inverting
input at zero volts (inputs equal).
For this condition to be met,
assuming that the feedback resistors
are of equal value, the output
voltage will always be equal to the
input voltage but of opposite
polarity.
For example, if the input (the free
end of R1) is at +2.67 volts the
output will be -2.67 volts. The gain
can be adjusted by changing the
ratio of the feedback resistor values.
Op Amp Applications:


Differential Amplifier
The differential amplifier has a
voltage divider on the noninverting input and another
voltage divider in the feedback
loop to the inverting input. R1
and R3 are of equal value and
that R2 and R4 are also of equal
value. When the operational
amplifier adjusts the output
voltage until the inverting and
non-inverting inputs are equal,
the output will always be the
difference between the two input
voltages (the free ends of R1 and
R3) if all of the feedback resistors
are equal. If the two input
voltages are equal, the output will
be zero volts. If voltage gain is
desired the ratios of the feedback
resistors can be changed.
Op Amp Applications:




DC Motor Control
Here is a simple practical application for
an operational amplifier. Assume that
the tachometer produces 1 volt for each
100 RPM of the motor.
If the potentiometer is set at 1 volt the
op-amp will adjust its output voltage
until the motor stabilizes at 100 RPM. If
the motor should slow down the opamp will increase its output voltage
until the motor returns to 100 RPM.
If the output impedance of the op-amp
is too high (and would be unable to
supply enough current to run the
motor) an NPN transistor can be
inserted between the op-amp and the
motor in an emitter-follower
configuration.
Op Amp Applications:


Current Controller
This is actually just the non-inverting
amplifier configuration. Assume that the
potentiometer is set at 1 volt. The op-amp
will adjust the output until 1 volt is seen at
the inverting input. This means that the
voltage across the sense resistor will be 1
volt regardless of the value of either
feedback resistor. The current in the
feedback loop can be selected by choosing
a sense resistor that has the desired current
at 1 volt. Since the load resistor is in series
with the sense resistor the current through
the Load resistor will be the same as the
current through the sense resistor
regardless of the value of the load resistor
(the voltage across the load resistor will
vary accordingly).
Power Supplies


A power supply is a circuit that changes one
power delivery system to be compatible with a
certain type of circuit. For example, the most
common type of power supply changes the 120
VAC available at the typical power receptacle to
some lower DC voltage. This is a DC power
supply.
There are four possible power supply stages:
A
A
A
A
voltage step-down
rectifier
filter
regulator (optional)
Voltage step-down



Voltage step-down is usually accomplished
with a transformer.
The stage is required to set the output
voltage with unregulated power supplies
and to reduce power loss in the regulator
of regulated power supplies.
Because of the high efficiency of switching
regulators this stage is not required in
switching
Filter



The filter will smooth-out the pulses
produced by the rectifier.
The most common filter is a capacitor
placed across the load.
Sometimes an inductor is also placed in
series with the load to help filter the
rectified output
Regulator



A regulator is an optional
stage when the demand is
heavy or variable or the
input source is not stable.
A standard regulator
requires a low input
voltage and produces a lot
of heat.
A switching regulator
produced little heat and
can work with high input
voltages.
A simple
regulator
The zener diode is chosen
to be 0.7 volts higher than
the desired output
frequency. The transistor
parameters are not critical
except that it must be able
to handle the power
necessary for the circuit.
Voltages in a power supply


The voltage at secondary of the
transformer would typically be
measured with an AC voltmeter and
therefore be displayed in RMS volts.
The voltage across the filter
capacitor and load would be the peak
voltage across the secondary of the
transformer minus any voltage lost
across the diodes in the rectifier.
Switching Power Supply



A switching power
supply switches the
pass transistor (as in
the simple regulator
above) so that it is
always either
completely on or
completely off.
The duration of the
pulses are varied to
control the average
output voltage.
The output voltage has
extreme ripple so
heavy filters are used
to smooth it.
Switching power supply
Radio Receivers




The first section is the RF amplifier. This section determines
the inherent noise level.
The mixer and local oscillator shift the received frequency
to the intermediate frequency
The IF amplifier must have correct bandwidth (frequency
response) in order to pass the desired signal and to reject
adjacent interference.
The Demodulator extracts the original base band signal
from the RF carrier.
Video Displays



The two most popular video displays are
the cathode ray tube (CRT) and the liquid
crystal display (LCD).
The CRT operates by sweeping a beam of
electrons across a phosphorus screen that
glows when hit by the electrons.
The LCD works by changing the
polarization of light as it passes between
cross-polarized filters.
Digital Measurements/Testing



There are a number of sophisticated instruments
for testing digital circuits.
The most common, and possibly most useful, is a
logic probe. A logic probe can be fairly
sophisticate or nothing more than an LED in a
clip-lead. It is used simply to see if the logic level
on a particular connection is a one or a zero.
A Logic pulser is Sometimes used to force circuit
inputs to the necessary levels for
troubleshooting. A logic pulser is simply a small
pulse generator.
Binary Numbers
First, create a table that
looks like this one.
Next, write the binary Finally, add up the
number in the table.
numbers that have
a 1 below them.
The sum is the
decimal equivalent
of the binary
number.
Converting Decimal to Binary
Binary Addition
There are four rules
for binary addition:
0
+0
0
0
+1
1
1
+ 1
0
1
1
1
+ 1
1
0+0=0
0 + 1 (or 1+0)
=1
1 + 1 = 0 and
carry over
to the next
column to
the left
1 + 1 + 1 (as with a carry
from the column to the
right) = 1 and a carry
over to the next
column to the left
1
Binary Addition (Cont’d)

The following two 8
bit numbers, when
added together,
show all the binary
addition rules in
action.
11
1
00110011
+00111010
01101101
Hexadecimal Numbers

Hexadecimal numbers are used as shorthand
for binary numbers. As you can see in the
table below, each four bit binary number has a
hexadecimal equivalent.
Hexadecimal

To convert any
binary number to
hexadecimal, break
the number into
groups of four and
write the
hexadecimal
equivalent for each
group.
16 bit binary
number
Broken into
groups of
four
—
101101001010110 1
— 1011 | 0100 | 1010 | 1101
Hexadecimal
for each
group
—
Final
Hexadecimal
number
—
B
|
4
|
A | D
B4AD
Logic Gates



Most digital circuits consist of logic
gates. These are representations
of the functions of circuits, rather
than the actual configurations.
The following gates are shown with
three inputs.
Logic gates can actually have any
number of inputs.
Logic Gates

The following four rules may be useful in
understanding how logic gates work:

OR Gate
• The output is a logical one if any of the inputs are a
logical one

AND Gate
• The output is a logical one if all of the inputs are a
logical one.

Exclusive OR (XOR) Gate
- The output is a logical one if there is any difference in
the inputs.
-
Inverter
• One input and one output. The output is always the
opposite of the input.
OR/NOR GATES
AND/NAND GATES
Exclusive OR / Exclusive NOR
Gates
Inverter or “Not”
Soldering

Unplated Tip
 Unplated tips are rare on soldering irons used in
electronics. Unplated tips can be cleaned with a file to
expose the bare copper. Then the iron should be heated
and coated with solder.

Plated Tip The favored method to clean a soldering iron tip is to
wipe the hot tip on a wet cellulose sponge. However,
according to the ETA also suggests a 320 grit aluminum
oxide cloth on a cold tip should be used. However, if you
suggest cleaning a plated soldering iron tip with emery
cloth to most technicians you will get a raised eyebrow
in return. Another method is to dip the hot tip in flux
then wipe it on a soft cloth.
Proper Soldering Techniques
Normal
Circuits
High
Voltage
Circuits
Make a good mechanical connection
Clean the soldering iron tip
Tin the tip (put enough solder on the tip to make good contact
with the joint)
Heat the joint, not the solder
Touch the solder to the joint, not the soldering iron
Use only as much solder as necessary for a good connection
Do not move the joint until the solder has solidified
Leave a smooth rounded covering of solder on connections.
Sharp points with high voltage can cause coronal discharge.
Questions?
Electrical Safety






Basics of Electricity:
Electrical current will not flow unless it has a
complete path (circuit) that returns to its source
(battery, transformer).
Current flows through you and other conductors,
such as metals, earth and concrete.
Current can harm you when it flows through your
body (electric shock).
Insulators resist the flow of electricity. Insulating
materials are used to coat copper conducting wires
and are used to make electrical work
gloves. Insulators help to protect humans from
coming into contact with electricity flowing through
conductors.
Just as there is pressure in a water pipe, even with
no water flowing, there is voltage at a receptacle,
even if current is not flowing. Another word for
voltage is "Potential."
Electrical Safety




How Electricity Can Harm You
Current passing through your body can cause electric
shock, resulting in 3 types of potential injuries:
Burns (arcs burn with heat & radiation)
Physical injuries (broken bones, falls, & muscle damage)
 At 10 mA, the muscles clamp on to whatever the person is
holding.

Nervous system effects (stop breathing at 30 to 75 mA
alternating current at 60Hz, fibrillation at 75 to 100 mA at
60Hz)
 Fibrillation = heart is "twitching" and there is no blood flow to
the body.




The heart can be damaged because it is in the path of the
most common routes electricity will take through the body:
Hand-to-hand
Hand-to-foot
Electrical Safety




Plan your work and plan for safety
Avoid wet working conditions and other dangers
Use Ground Fault Circuit Interrupters. GFCI's are
electrical devices that are designed to detect
ground faults (when current is "leaking"
somewhere outside its intended pathway). If
your body provides the path to ground for the
leaking current, you could receive a shock or be
electrocuted. GFCI's should be used in all wet
locations and on outside outlets.
Avoid overhead power lines: Position yourself
so that the longest conductive object you are
using (saws, poles, tools, brooms, etc.) cannot
come closer than at least 10 feet to any
unguarded, energized overhead line.
Electrical Safety


Use proper wiring and connectors
Use extension cords properly and
temporarily:
Cords must be UL listed and have 3 prongs
Power bars must have a fuse or breaker
Do not use 2-prong, ungrounded cords in a lab
Do not run cords through walls, doors, under
rugs, or across aisles
Do not repair cords--buy new ones
Make sure the total number of watts connected
to the cord does not exceed the rating of the
cord.
Electrical Safety



Use and maintain tools properly
Avoid wearing items such as jewelry,
watch bands, bracelets, rings, key
chains, necklaces, etc. that might
come into contact with exposed,
energized parts.
Wear correct PPE:
Hard hats rated "Class E"
ANSI-approved footwear coded "EH"
Safe Equipment










Do not use equipment that has been damaged or
improperly modified.
Always use equipment according to the manufacturer's
specifications.
"Live" parts (greater than 50 volts) must be guarded by
one or more of the following:
An enclosure that requires a tool for access.
A locked enclosure.
An interlocked access door.
A substantial insulating guard to prevent contact.
Check cords--they should:
Be completely free of damage and deterioration.
Should always have an appropriate strain relief device
where they enter the enclosure.
Electrical Safety
SAFETY FIRST, SAFETY ALWAYS!!
Questions?