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Electronics
Introduction to Electronics
The Electronic system
 Electric system : any technical system is an assembly of
components that are connected together to form a
functioning machine or an operational procedure . An
electronic system includes some common used electrical
devices such as resistors , capacitors, transformers ,
inductors , and few classes of semiconductors ( diodes ,
transistors )
The current in conductor and insulator
Voltage, current, and resistance
 Voltage : v and sometimes E
It’s equal to the work done to move the electric charge from
the negative point to the positive point and it’s measured in
volt.
 The electron charge is equal to 6*1018
 Current : I , the rate of flow of electric charge past from the
negative to the positive point and measured in ampere or
amp
 The same current into point in a circuit equals to the sum of
the currents out from the circuit ( kirchhoff current law)
 A node is any point in the circuit
 The sum of voltage drops around any closed circuit is zero (
kirchhoff voltage law)
Risistors
Resistance
 1-It has 2 kinds ,constant resistance and variable
resistance that I control it by changing its value .
 2-we can measure it using avometers .
 3- It's job to decrease the current as a lot of application if
don’t use resistance the system failure or corrupt .The law
wish depend on it is ohm’s low V=I*R .V is constant but
when R increase the current will decrease so as to the volt
must be const
 Calculate the value of the next resistors
Semiconductors
semiconductors
A semiconductor is a material which has electrical
conductivity between that of a conductor such as copper
and an insulator such as glass. The conductivity of a
semiconductor increases with increasing temperature,
behavior opposite to that of a metal. Semiconductors can
display a range of useful properties such as passing current
more easily in one direction than the other. Because the
conductive properties of a semiconductor can be modified
by controlled addition of impurities or by the application of
electrical fields or light, semiconductors are very useful
devices for amplification of signals, switching, and energy
conversion. Understanding the properties of
semiconductors relies on quantum physics to explain the
motions of electrons through a lattice of atoms.
Semiconductors
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A semiconductor is a material which has electrical conductivity between that of a conductor such as copper and
an insulator such as glass. The conductivity of a semiconductor increases with increasing temperature, behavior
opposite to that of a metal.
Semiconductors can display a range of useful properties such as passing current more easily in one direction than
the other. Because the conductive properties of a semiconductor can be modified by controlled addition of
impurities or by the application of electrical fields or light, semiconductors are very useful devices for
amplification of signals, switching, and energy conversion. Understanding the properties of semiconductors relies
on quantum physics to explain the motions of electrons through a lattice of atoms.
Current conduction in a semiconductor occurs via free electrons and "holes", collectively known as charge
carriers. Adding impurity atoms to a semiconducting material, known as "doping", greatly increases the number
of charge carriers within it. When a doped semiconductor contains excess holes it is called "p-type", and when it
contains excess free electrons it is known as "n-type". The semiconductor material used in devices is doped under
highly controlled conditions to precisely control the location and concentration of p- and n-type dopants. A single
semiconductor crystal can have multiple p- and n-type regions; the p-n junctions between these regions have many
useful electronic properties.
Semiconductors are the foundation of modern electronics, including radio, computers, and telephones.
Semiconductor-based electronic components include transistors, solar cells, many kinds of diodes including the
light-emitting diode (LED), the silicon controlled rectifier, photo-diodes, and digital and analog integrated
circuits. Increasing understanding of semiconductor materials and fabrication processes has made possible
continuing increases in the complexity and speed of semiconductor devices, an effect known as Moore's Law.
The Semiconductor Industry
 Semiconductor devices such as diodes, transistors and integrated
circuits can be found everywhere in our daily lives, in Walkman,
televisions, automobiles, washing machines and computers. We
have come to rely on them and increasingly have come to expect
higher performance at lower cost.
 Personal computers clearly illustrate this trend. Anyone who
wants to replace a three to five year old computer finds that the
trade-in value of his or her computer is surprising low. On the
bright side, one finds that the complexity and performance of the
today’s personal computers vastly exceeds that of their old
computer and that for about the same purchase price, adjusted for
inflation.
intrinsic semiconductor
 As a result of the thermal energy present in the material,
electrons can break loose from covalent bonds and become
free electrons able to move through the solid and contribute
to the electrical conductivity. The covalent bonds left behind
have an electron vacancy called a hole. Electrons from
neighboring covalent bonds can easily move into an
adjacent bond with an electron vacancy, or hole, and thus the
hold can move from one covalent bond to an adjacent bond.
As this process continues, we can say that the hole is moving
through the material
Doped semiconductor
 A semiconductor that has had impurity atoms
added to modify the electrical conduction
characteristics.
Extrinsic semiconductor
 A semiconductor that has been doped with
impurities to modify the electrical conduction
characteristics.
Hole
 An electron vacancy in a covalent bond between
two atoms in a semiconductor. Holes are mobile
charge carriers with an effective charge that is opposite to
the charge on an electron.
P-N
 N-type semiconductor: A semiconductor that has
been doped with donor impurities to produce the
condition that the population of free electrons is greater than
the population of holes.
 P-type semiconductor: A semiconductor that has
been doped with acceptor impurities to produce
the condition that the population of holes is greater than the
population of free electrons.
p-n Junctions
 P-n junctions consist of two semiconductor regions of
opposite type. Such junctions show a pronounced rectifying
behavior. They are also called p-n diodes in analogy with
vacuum diodes.
 The p-n junction is a versatile element, which can be used as
a rectifier, as an isolation structure and as a voltagedependent capacitor. In addition, they can be used as solar
cells, photodiodes, light emitting diodes and even laser
diodes. They are also an essential part of Metal-Oxide-Silicon
Field-Effects-Transistors (MOSFETs) and Bipolar Junction
Transistors (BJTs).
Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol shows
the direction in which the current can flow. Diodes are the electrical version of a valve and
early diodes were actually called valves.
Properties of a p–n junction
 The p–n junction possesses some interesting properties that have
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useful applications in modern electronics. A p-doped
semiconductor is relatively conductive. The same is true of an ndoped semiconductor, but the junction
between them can become depleted of charge carriers, and hence
non-conductive, depending on the relative voltages
of the two semiconductor regions. By manipulating this nonconductive layer, p–n junctions are commonly used as
diodes: circuit elements that allow a flow of electricity in one
direction but not in the other (opposite) direction. This
property is explained in terms of forward bias and reverse bias, where
the term bias refers to an application of
electric voltage to the p–n junction.
Forward bias
 In forward bias, the p-type is connected with the positive
terminal and the n-type is connected with the negative
terminal.
Forward bias
 With a battery connected this way, the holes in the P-type region and the
electrons in the N-type region are pushed toward the junction. This
reduces the width of the depletion zone.
 The positive charge applied to the P-type material repels the holes,
while the negative charge applied to the N-type material repels the
electrons. As electrons and holes are pushed toward the junction, the
distance between them decreases. This lowers the barrier in potential.
 With increasing forward-bias voltage, the depletion zone eventually
becomes thin enough that the zone's electric field cannot counteract
charge carrier motion across the p–n junction, as a consequence
reducing electrical resistance. The electrons that cross the p–n junction
into the P-type material (or holes that cross into the N-type material)
will diffuse in the near-neutral region. Therefore, the amount of
minority diffusion in the near-neutral zones determines the amount of
current that may flow through the diode.
Reverse bias
 Reverse-bias usually refers to how a diode is used in a circuit.
 Therefore, no current will flow until the diode breaks down.
Connecting the P-type region to the negative terminal of the
battery and the N-type region to the positive terminal corresponds to
reverse bias.
Reverse bias
 Because the p-type material is now connected to the negative
terminal of the power supply, the 'holes' in the P-type material are
pulled away from the junction, causing the width of the depletion
zone to increase. Likewise, because the N-type region is
connected to the positive terminal, the electrons will also be
pulled away from the junction. Therefore, the depletion region
widens, and does so increasingly with increasing reverse-bias
voltage. This increases the voltage barrier causing a high resistance
to the flow of charge carriers, thus allowing minimal electric
current to cross the p–n junction. The increase in resistance of the
p–n junction results in the junction behaving as an insulator.
Types Of Diodes
How are the Diode Work
Zener diode
 A Zener diode is a diode which allows current to flow in
the forward direction in the same manner as an ideal diode,
but will also permit it to flow in the reverse direction when
the voltage is above a certain value known as the breakdown
voltage
Zener diode
 Zener diode is a special purpose P-N junction diode. It was
invented by Clarence Zener. A zener diode works as a normal
P-N junction diode in the forward biased condition. The
specialty is that, it is designed to operate in the reverse biased
condition! The normal diode will not allow current flow in
the reverse biased condition, and if the reverse voltage
exceeds the breakdown voltage, the diode may get
permanently damaged. But the zener diode will not damage,
even if the reverse voltage exceeds the breakdown value. The
voltage across the zener diode will stay stable, irrespective of
the input voltage. So the zener diode is ideal for applications
requiring stabilized voltages.
 http://www.wainet.ne.jp/~yuasa/flash/EngPnJunction.swf
 http://www-
g.eng.cam.ac.uk/mmg/teaching/linearcircuits/diode.html
Avalanche Effect (breakdown)
 Zener diodes are used with reverse bias, making use
of the breakdown
 that occurs across a silicon junction when the reverse voltage
causes a large electrostatic field to develop across the
junction. This breakdown limit occurs at low voltages (below
6 V) when the silicon is very strongly doped, and such
breakdown is termed Zener breakdown, from Clarence
Zener who discovered the effect. For such a true Zener diode
Summary
 The forward-bias and the reverse-bias properties of the p–n
junction imply that it can be used as a diode. A p–n junction
diode allows electric charges to flow in one direction, but
not in the opposite direction; negative charges (electrons)
can easily flow through the junction from n to p but not from
p to n, and the reverse is true for holes.
 When the p–n junction is forward-biased, electric charge
flows freely due to reduced resistance of the p–n junction.
 When the p–n junction is reverse-biased, however, the
junction barrier (and therefore resistance) becomes greater
and charge flow is minimal.
Review Questions
 State the difference between the forward bias and the reverse
bias?
 What are the main types of Diodes ? Briefly describe?
 What is meant by :
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Crystal
Recombination
Intrinsic Semiconductors
Extrinsic semiconductor
Avalanche Effect
Zener Diode
Review Questions
 What is meant by P-N Junction?
 Explain the difference between the P-type and the N-type?
 What is meant by Hole?
 What is meant by breakdown voltage?
 State the difference between the donor and the accepter
Junctions?
Review Questions
 Define the Semiconductors and doped semiconductors?
 Define the depletion layer ?
 State the major usage of semiconductors in industry?
 Illustrate the covalent bond , with figures?
Transistors
 The transistor is our most important example of an "active"
component, a device that can amplify, producing an output signal
with more power in it than the input signal.
Transistors
Transistor usage
 The transistors used in all the electronic circuit because it’s
ability to control the current flow in the circuit . This circuits
such as:
1)
2)
3)
4)
5)
electronic switch
digital electronic circuits
Registers
flip-flops
Amplifiers
Types of Transistors
Bipolar Junction Transistor
Bipolar junction transistor
 A bipolar junction transistor (BJT or bipolar
transistor) is a type of transistor that relies on the
contact of two types of semiconductor for its operation.
BJTs can be used as amplifiers, switches, or in oscillators.
BJTs can be found either as individual discrete components,
or in large numbers as parts of integrated circuits.
 Bipolar transistors are so named because their operation involves both
electrons and holes.These two kinds of charge carriers are
characteristic of the two kinds of doped semiconductor
material. In contrast, unipolar transistors such as the fieldeffect transistors have only one kind of charge carrier.
Bipolar junction transistor
Bipolar junction transistor
How bipolar transistors are used
How bipolar transistors are used
Transport Factor
‫‪The Current gain‬‬
‫نسبة تيار المجمع أو الباعث على تيار القاعدة بكسب الترانزستور (‪)transistor gain‬‬
Darlington transistor
Power bipolar junction transistor
Field Effect Transistors (FET)