Download EECE 1101 Lab Manual

ELECTRICAL ENGINEERING
LAB I
EECE 1101 - LAB MANUAL
SEMESTER II 2016/2017
NAME:
MATRIC NO:
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TABLE OF CONTENT
Dress Codes and Ethics ................................................................................................... - 3 Safety .............................................................................................................................. - 4 Acquaint yourself with the location of the following safety items within the lab. ..... - 4 Electric shock .............................................................................................................. - 4 Equipment grounding.................................................................................................. - 5 Precautionary Steps before Starting an Experiment ................................................... - 7 INTRODUCTION TO ELECTRICAL ENGINEERING LAB I (EECE 1101) ............ - 9 1. Basic Guidelines ..................................................................................................... - 9 2. Lab Instructions ...................................................................................................... - 9 3. Grading ................................................................................................................. - 10 4. Lab Reports ........................................................................................................... - 10 a. Report format and Evaluation: .......................................................................... - 10 b. Presentation of Lab Reports: ............................................................................. - 12 5. Schedule & Experiment No. (Title) ...................................................................... - 13 6. Lab Components ................................................................................................... - 14 Resistor ................................................................................................................. - 14 Variable resistors .................................................................................................. - 15 Digital Multi-meter (DMM) ................................................................................. - 16 Function Generators .............................................................................................. - 17 Oscilloscope .......................................................................................................... - 18 EXPERIMENT 1: Ohm’s Law & Series and Parallel Circuits .................................. - 21 EXPERIMENT 2: Kirchhoff’s Voltage and Current Laws ....................................... - 25 EXPERIMENT 3: Verification of Superposition Theorem ....................................... - 28 EXPERIMENT 4: Thevenin’s & Norton’s Theorem and Maximum Power Transfer
Theorem ....................................................................................... - 30 EXPERIMENT 5: Diode Characteristic and Application .......................................... - 34 EXPERIMENT 6: BJT Characteristics & Biasing Circuits ....................................... - 37 EXPERIMENT 7: MOSFET – Common-Source Amplifier...................................... - 40 EXPERIMENT 8: Inverting and Non-inverting Op-Amp ......................................... - 43 -
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Dress Codes and Ethics
24:31 And say to the believing women that they should lower their gaze and
guard their modesty; that they should not display their beauty and
ornaments except what (must ordinarily) appear thereof; that they should
draw their veils over their bosoms and not display their beauty except to
their husbands, their fathers, their husband's fathers, their sons, their
husbands' sons, their brothers or their brothers' sons, or their sisters' sons,
or their women, or the slaves whom their right hands possess, or male
servants free of physical needs, or small children who have no sense of the
shame of sex; and that they should not strike their feet in order to draw
attention to their hidden ornaments. And O ye Believers! turn ye all together
towards Allah, that ye may attain Bliss.
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Safety
Safety in the electrical laboratory, as everywhere else, is a matter of the knowledge of
potential hazards, following safety precautions, and common sense. Observing safety
precautions are important due to pronounced hazards in any electrical/computer
engineering laboratory. Death is usually certain when 0.1 ampere or more flows through
the head or upper thorax and have been fatal to persons with coronary conditions. The
current depends on body resistance, the resistance between body and ground, and the
voltage source. If the skin is wet, the heart is weak, the body contact with ground is large
and direct, then 40 volts could be fatal. Therefore, never take a chance on "low" voltage.
When working in a laboratory, injuries such as burns, broken bones, sprains, or damage
to eyes are possible and precautions must be taken to avoid these as well as the much less
common fatal electrical shock. Make sure that you have handy emergency phone
numbers to call for assistance if necessary. If any safety questions arise, consult the lab
demonstrator or technical assistant/technician for guidance and instructions. Observing
proper safety precautions is important when working in the laboratory to prevent harm to
yourself or others. The most common hazard is the electric shock which can be fatal if
one is not careful.
Acquaint yourself with the location of the following safety items within the lab.
a. fire extinguisher
b. first aid kit
c. telephone and emergency numbers
03-6196 4530
ECE Department
Kulliyyah
of
Engineering
03-6196 4410
Deputy Dean’s Student Affairs
IIUM Security
03-6196 5555
IIUM Clinic
03-6196 4444
Electric shock
Shock is caused by passing an electric current through the human body. The severity
depends mainly on the amount of current and is less function of the applied voltage. The
threshold of electric shock is about 1 mA which usually gives an unpleasant tingling. For
currents above 10 mA, severe muscle pain occurs and the victim can't let go of the
conductor due to muscle spasm. Current between 100 mA and 200 mA (50 Hz AC)
causes ventricular fibrillation of the heart and is most likely to be lethal.
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What is the voltage required for a fatal current to flow? This depends on the skin
resistance. Wet skin can have a resistance as low as 150 Ohm and dry skin may have a
resistance of 15 kOhm. Arms and legs have a resistance of about 100 Ohm and the trunk
200 Ohm. This implies that 240 V can cause about 500 mA to flow in the body if the skin
is wet and thus be fatal. In addition skin resistance falls quickly at the point of contact, so
it is important to break the contact as quickly as possible to prevent the current from
rising to lethal levels.
Equipment grounding
Grounding is very important. Improper grounding can be the source of errors, noise and a
lot of trouble. Here we will focus on equipment grounding as a protection against
electrical shocks. Electric instruments and appliances have equipment casings that are
electrically insulated from the wires that carry the power. The isolation is provided by the
insulation of the wires as shown in the figure a below. However, if the wire insulation
gets damaged and makes contact to the casing, the casing will be at the high voltage
supplied by the wires. If the user touches the instrument he or she will feel the high
voltage. If, while standing on a wet floor, a user simultaneously comes in contact with the
instrument case and a pipe or faucet connected to ground, a sizable current can flow
through him or her, as shown in Figure b. However, if the case is connected to the ground
by use of a third (ground) wire; the current will flow from the hot wire directly to the
ground and bypass the user as illustrated in Figure c.
Equipment with a three wire cord is thus much safer to use. The ground wire (3rd wire)
which is connected to metal case is also connected to the earth ground (usually a pipe or
bar in the ground) through the wall plug outlet.
Always observe the following safety precautions when working in the laboratory:
1. Do not work alone while working with high voltages or on energized electrical
equipment or electrically operated machinery like a drill.
2. Power must be switched off whenever an experiment or project is being assembled,
disassembled, or modified. Discharge any high voltage points to grounds with a wellinsulated jumper. Remember that capacitors can store dangerous quantities of
energy.
3. Make measurements on live circuits or discharge capacitors with well insulated probes
keeping one hand behind your back or in your pocket. Do not allow any part of your body
to contact any part of the circuit or equipment connected to the circuit.
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4. After switching power off, discharge any capacitors that were in the circuit. Do not trust
supposedly discharged capacitors. Certain types of capacitors can build up a residual
charge after being discharged. Use a shorting bar across the capacitor, and keep it
connected until ready for use. If you use electrolytic capacitors, do not :
 put excessive voltage across them
 put ac across them
 connect them in reverse polarity
5. Take extreme care when using tools that can cause short circuits if accidental contact is
made to other circuit elements. Only tools with insulated handles should be used.
6. If a person comes in contact with a high voltage, immediately shut off power. Do not
attempt to remove a person in contact with a high voltage unless you are insulated from
them. If the victim is not breathing, apply CPR immediately continuing until he/she is
revived, and have someone dial emergency numbers for assistance.
7. Check wire current carrying capacity if you will be using high currents. Also make sure
your leads are rated to withstand the voltages you are using. This includes instrument
leads.
8. Avoid simultaneous touching of any metal chassis used as an enclosure for your circuits
and any pipes in the laboratory that may make contact with the earth, such as a water
pipe. Use a floating voltmeter to measure the voltage from ground to the chassis to see if
a hazardous potential difference exists.
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9. Make sure that the lab instruments are at ground potential by using the ground terminal
supplied on the instrument. Never handle wet, damp, or ungrounded electrical equipment.
10.
Never touch electrical equipment while standing on a damp or metal floor.
11.
Wearing a ring or watch can be hazardous in an electrical lab since such items make good
electrodes for the human body.
12.
When using rotating machinery, place neckties or necklaces inside your shirt or, better
yet, remove them.
13.
Never open field circuits of D-C motors because the resulting dangerously high speeds
may cause a "mechanical explosion".
14.
Keep your eyes away from arcing points. High intensity arcs may seriously impair your
vision or a shower of molten copper may cause permanent eye injury.
15.
Never operate the black circuit breakers on the main and branch circuit panels.
16.
In an emergency all power in the laboratory can be switched off by depressing the
large red button on the main breaker panel. Locate it. It is to be used for
emergencies only.
17.
Chairs and stools should be kept under benches when not in use. Sit upright on
chairs or stools keeping the feet on the floor. Be alert for wet floors near the stools.
18.
Horseplay, running, or practical jokes must not occur in the laboratory.
19.
Never use water on an electrical fire. If possible switch power off, and then use CO2
or a dry type fire extinguisher. Locate extinguishers and read operating instructions
before an emergency occurs.
20.
Never plunge for a falling part of a live circuit such as leads or measuring equipment.
21.
Never touch even one wire of a circuit; it may be hot.
22.
Avoid heat dissipating surfaces of high wattage resistors and loads because they can
cause severe burns.
23.
Keep clear of rotating machinery.
Precautionary Steps before Starting an Experiment
a)
Read materials related to experiment beforehand as preparation for pre-lab quiz and
experimental calculation.
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b)
Make sure that apparatus to be used are in good condition. Seek help from technicians
or the lab demonstrator in charge should any problem arises.
 Power supply is working properly ie Imax (maximum current) LED indicator is
disable. Maximum current will retard the dial movement and eventually damage the
equipment. Two factors that will light up the red LED indicator are short circuit and
insufficient supply of current by the equipment itself. To monitor and maintain a
constant power supply, the equipment must be connected to circuit during voltage
measurement. DMM are not to be used simultaneously with oscilloscope to avert
wrong results.
 Digital multimeter (DMM) with low battery indicated is not to be used. By proper
connection, check fuses functionality (especially important for current measurement).
Comprehend the use of DMM for various functions. Verify measurements obtained
with theoretical values calculated as it is quite often where 2 decimal point reading
and 3 decimal point reading are very much deviated.
 The functionality of voltage waveform generators are to be understood. Make sure
that frequency desired is displayed by selecting appropriate multiplier knob. Improper
settings (ie selected knob is not set at minimum (in direction of CAL – calibrate) at
the bottom of knob) might result in misleading values and hence incorrect results.
Avoid connecting oscilloscope together with DMM as this will lead to erroneous
result.
 Make sure both analog and digital oscilloscopes are properly calibrated by
positioning sweep variables for VOLT / DIV in direction of CAL. Calibration can
also be achieved by stand-alone operation where coaxial cable connects CH1 to
bottom left hand terminal of oscilloscope. This procedure also verifies coaxial cable
continuity.
c)
Internal circuitry configuration of breadboard or Vero board should be at students’
fingertips (ie holes are connected horizontally not vertically for the main part with
engravings disconnecting in-line holes).
Students should be rest assured that measured values (theoretical values) of discrete
components retrieved ie resistor, capacitor and inductor are in accordance the required
ones.
d)
e)
Continuity check of connecter or wire using DMM should be performed prior to an
experiment. Minimize wires usage to avert mistakes.
f)
It is unethical and unislamic for students to falsify results as to make them appear
exactly consistent with theoretical calculations.
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INTRODUCTION TO ELECTRICAL ENGINEERING LAB I
(EECE 1101)
1.
2.
3.
4.
5.
6.
Basic Guidelines
Lab Instructions
Grading
Lab Reports
Schedule and Experiment No. (Title)
Lab Components
1. Basic Guidelines
All experiments in this manual have been tried and proven and should give you little
trouble in normal laboratory circumstances. However, a few guidelines will help you
conduct the experiments quickly and successfully.
i.
ii.
iii.
iv.
v.
Each experiment has been written so that you follow a structured logical sequence meant
to lead you to a specific set of conclusions. Be sure to follow the procedural steps in the
order which they are written.
Read the entire experiment and research any required theory beforehand. Many times an
experiment takes longer that one class period simply because a student is not well
prepared.
Once the circuit is connected, if it appears “dead’’ spend few moments checking for
obvious faults. Some common simple errors are: power not applied, switch off, faulty
components, lose connection, etc. Generally the problems are with the operator and not
the equipment.
When making measurements, check for their sensibility.
It’s unethical to “fiddle” or alter your results to make them appear exactly
consistent with theoretical calculations.
2. Lab Instructions
i.
ii.
iii.
iv.
v.
vi.
Each student group consists of a maximum of three students. Each group is responsible in
submitting one (1) lab report upon completion of each experiment.
Students are to wear proper attire i.e shoe or sandal instead of slipper. Excessive
jewelleries are not advisable as they might cause electrical shock.
Personal belongings i.e bags, etc are to be put at the racks provided. Student groups are
required to wire up their circuits in accordance with the diagram given in each
experiment.
A permanent record in ink of observations as well as results should be maintained by
each student and enclosed with the report.
The recorded data and observations from the lab manual need to be approved and
signed by the lab instructor upon completion of each experiment.
Before beginning connecting up, it is essential to check that all sources of supply at the
bench are switched off.
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vii.
viii.
ix.
x.
Start by connecting up the experiment circuit by wiring up the main circuit path, and then
add the parallel branches as indicated in the circuit diagram.
After the circuit has been connected correctly, remove all unused leads from the
experiment area, set the voltage supplies at the minimum value, and check the meters are
set for the intended mode of operation.
The students may ask the lab instructor to check the correctness of their circuit before
switching on.
When the experiment has been satisfactory completed and the results approved by the
instructor, the students may disconnect the circuit and return the components and
instruments to the locker tidily. Chairs are to be slid in properly.
3. Grading
The work in the Electronics related lab carries 45% of total marks for the EECE 1101
subject (ENGINEERING LAB II). The distribution of marks for Electronics Lab is as
follows:
Lab Report
40%
Quiz
20%
Final Test
40%
Total
100%
4. Lab Reports
a. Report format and Evaluation:
The following format should be adhered to by the students in all their laboratory reports:
Experiment
1-4
Marks
20%
No.
Evaluation Items
1
2
3
Objectives
Experiment Set-up
Results/Observations
Discussion and
Conclusion
TOTAL
20
4
Marks
Obtain
No.
Evaluation Items
2
4
5
1
2
3
9
4
Objectives
Experiment Set-up
Results/Observations
Discussion and
Conclusion
PSPICE
TOTAL
5
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Experiment
5-8
Marks
20%
2
4
4
6
4
20
Marks
obtain
Evaluation Criteria
Range of scores
0
7
8
9
10
11
12
13
14
15
17
6.5
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
16.5
20
Grade
F
E
DD
C
C+
BB
B+
AA
Poor
Fair
Good
Very Good
Excellent
Of those listed above each section included in a report should be clearly nominated with
the appropriate heading. The information to be given in each section is set out below:
(i) Objective
This should state clearly the objective of the experiment. It may be the verification of
law, a theory or the observation of particular phenomena. Writing out the objective of the
experiment is important to the student as it emphasizes the purpose for which the
experiment is conducted.
(ii) Experiment Set-up
In this section, the list of equipment used in the experiment must be listed and the circuit
has to be drawn for each part of the experiment.
(iii) Results/Observations
All experimental results which have been approved by the lab instructor (including
graphs) must be attached in the report.
(iv) PSPICE
PSPICE output (as instructed in the lab manual) must be attached in the report to show
the comparison of simulation results and experimental results.
(v) Discussion & Conclusion
Once the analysis of the results is complete, the student must forms some deductions on
the results of his analysis. Usually this involves deducing whether the final results show
that the aim of the experiment has been achieved or not, and if they verify some law or
theory presented to the student during the lectures. This is where some brief theory
can be included. Comments and comparison asked in the lab manual must be
discussed in this section.
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The student should give considerable thought to the material that he intends to submit in
this section. It is here that he is able to express his own ideas on the experiment results
and how they were obtained. It is the best indication to his teacher of whether he has
understood the experiment and of how well he has been able to analyze the results and
make deductions from them.
It is recommended that the conclusion should be taken up by the student’s clear and
concise explanation of his reasoning, based on the experimental results, which led to the
deductions.
It is very rare for an experiment to have results which are entirely without some
discrepancy. The student should explain what factors, in his opinion, may be the possible
causes of these discrepancies. Similarly, results of an unexpected nature should form the
basis for a discussion of their possible nature and cause.
The student should not be reluctant to give his opinions even though they may not be
correct. He should regard his discussion as an opportunity to demonstrate his reasoning
ability.
Should the results obtained be incompatible with the aim or with the theory underlying
the experiment, then an acceptable report may be written suggesting reasons for the
unsatisfactory results. It is expected that the student should make some suggestions as to
how similar erroneous results for this experiment might be avoided in the future. The
student must not form the opinion that an unsatisfactory set of results makes a report
unacceptable.
b. Presentation of Lab Reports:
All students are required to present their reports in accordance with the following
instructions.
i.
Reports have to be handwritten for submission. The report writing should be rotated
between members of the group.
ii.
Writing should appear on one side of each sheet only.
iii.
The students’ name & matric number, section number, lab session and the lecturer’s
name must be printed in block letters at the top left-hand corner of the first sheet of the
report. This must be followed in the middle of the sheet by:
 The course code
 The experiment number
 The title of the experiment
 The date on which the student carried out the experiment.
iv.
All sections such as objective, experiment set-up and so on, should be titled on the left
hand side of the working space of the page.
v.
Take note on these results formatting:
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
vi.
vii.
Each type of calculation pertaining to the experiment should be preceded by a brief
statement indicating its objective.
 All calculations are to be shown in sufficient details to enable the reader to follow
their procedure.
 All formulas used are to be written in correct symbols prior to the substitution of the
known quantities.
All graphs are to be drawn on graph paper in blue or black ink. Other colors may be used
for identification. The abscissa and ordinate are to be drawn in all times and scaled with
the value clearly indicated at each major division. The quantity at each axis represents
and the unit in which it is calibrated should be clearly indicated. Each graph is to be titled
so as to indicate clearly what it represents.
The report submitted by each student should contain a Discussion and Conclusion section
that has more than 300 words.
5. Schedule & Experiment No. (Title)
Content Outlines
Weeks
Topics
Task/Reading
1
Introduction to Lab
2
3
4
Experiment #1: Ohm’s Law & Series and parallel
circuits
5
Experiment #3: Thevenin’s and Norton’s theorem
and Maximum power transfer theorem
Experiment #4: Superposition Theorem
Introduction to Simulation Software PSPICE
6
7
8
Experiment #2: Kirchoff’s voltage and current laws Experiment #2
12
Experiment #5: Diode Characteristic and
Application
Experiment #6: BJT Characteristic and Biasing
Circuits
Experiment #7: MOSFET - Common Source
Amplifier
Experiment #8: Inverting and Non-Inverting OpAmp
Preparation Week
13
Any additional make-up lab if necessary
14
Final Test
9
10
11
Experiment #1
Experiment #3
Experiment #4
Experiment #5
Experiment #6
Experiment #7
Experiment #8
All lab reports should be submitted upon starting the lab session of the following week
to the lecturer/demonstrators on duty for your section. Late submission of the lab report
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will not be entertained and will be given Nil for the report. Strictly no make up lab due
to absenteeism is allowed without sound reason.
6. Lab Components
Resistor
The ohm is the unit of resistance, and it is represented by the symbol Ω (Greek letter
omega). Resistance values are indicated by a standard color code that manufacturers have
adopted. This code uses color band on the body of resistor. The colors and their
numerical values are given in the resistor color chart, Table A. This code is used for 1/8w, 1/4-w, 1/2- w, 2-w, and 3-w resistors.(w stands for watt, i.e.is the power dissipation
ability of the resistance).
The basic resistor is shown in Fig. A. The standard color code marking consists of four
bands around the body of the resistor. The color of the first band indicates the first
significant figure of the resistance value. The second band indicates the second
significant figure. The color of the third band indicates the number of zeros that follow
the first two significant figures. For example: 1 kΩ color codes are arranged from the
leftmost to the rightmost to be brown, black, red and gold.
The fourth band indicates the percent tolerance of the resistance. Percent tolerance in the
amount the resistance may vary from the value indicated by the color code. Because
resistors are mass produced, variations in materials will affect their actual resistance.
Many circuits can still operate as designed even if the resistors in the circuit do not have
the precise value specified. Tolerances are usually given as plus or minus the nominal, or
color code value.
Wire wound, high-wattage resistors usually are not color coded but have the resistance
value and wattage rating printed on the body of resistor. To avoid having to write all the
zeros for high value resistors the metric abbreviations of k (for 1000) and M for
(1000000) are used. For example:
 33,000 Ω can be written as 33 kΩ. (pronounced 33 kay, or 33 kilohms)
 1,200,000 Ω can be written as 1.2 MΩ. (Pronounced 1.2 meg, or 1.2 megohms).
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Table A: Resistor color code
Color
Significant figure No. of Zeros (Multiplier) %Tolerance
(First & second band)
(third band)
(Forth band)
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Gray
White
Gold
Silver
No color
0(100)
1(101)
2(102)
3(103)
4(104)
5(105)
6(106)
7(107)
8(108)
9(109)
-1(10-1)
-2(10-2)
-
0
1
2
3
4
5
6
7
8
9
-
5
10
20
Lead
Tolerance
No. of zeros
First significant bit
Second significant bit
Fig. A: resistor color code
Variable resistors
In addition to the fixed-value resistors, variable resistors are used. The two types of
variable resistors are the rheostat and the potentiometer. Volume controls used in radio is
a typical example of potentiometer.
A rheostat is essentially a two-terminal device. Its circuit symbol is shown in Fig. B.
Points a and b are connected to the circuit. A rheostat has a maximum resistance value,
specified by the manufacturer, and a minimum value, usually 0Ω. The arrow head
indicates a mechanical means of adjusting the rheostat so that the resistance, measured
between points a and b, can be adjusted to any intermediate value within the range of
variation.
Fig. B
The circuit symbol of potentiometer, Fig C, shows that this is a three-terminal device.
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The resistance between the terminals a and c is fixed. Point b is the variable arm of the
potentiometer, the wiper. The arm is a metal contactor that slides along the un-insulated
surface of the resistance element. The resistance between points a and c varies as the
length of element included between points a and b. The same is true for points c and b.
Fig. C
A potentiometer may be used as a rheostat if the center arm and one of the end terminals
are connected into the circuit and the other end terminal is left disconnected.
Digital Multi-meter (DMM)
(i) Voltage/Resistance Measurements


A voltmeter must always be connected with probes across the component
under test; that is, the circuit need never be broken (see Fig. D). This is often
referred to as parallel connection.
Polarity: It is a good practice to place the correct leads at the proper nodes.
e.g.. Red lead at the positive node and the black lead at the negative node.
Fig. D - DMM measurement in parallel
(ii) Current Measurements

In measuring current (Fig. E) the meter must always be inserted within the
circuit in such a manner that the current to be measured will flow through
the meter and it is similar to a series connection. You must break the circuit
to perform a current measurement.
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Fig. E – DMM in series to measure current
Function Generators
Function generators (shown in Fig. F) is used to produce signal sources with a specifiable
voltage applied over a specifiable time. The signal can be of several types such as a sine
wave, triangle wave, or square wave depending on the model of the function generators.
Fig. F –Function Generator
Some common features for function generators are:
i. Selection to choose waveform type such as the sine, square, or triangle. Some
advanced model allows users to give ramps, pulses, or allow users to program a
particular arbitrary shape.
ii. Selection to choose the waveform frequency. The typical frequency ranges used
for electronic experiments are from 0.01 Hz to 10 MHz. Specific frequency range
can also be set through input button available on certain models.
iii. Selection for the waveform amplitude.
Fig. G is showing where these settings can be performed.
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Fig. G – Input settings for a function generator
There are also outlets for the output signal as shown in Fig. H. There are usually two
outputs:
i. The main output is the desired waveform set by the users. Typically, the signal has a
maximum voltage of 20 Volts peak-to-peak, or ±10 Volts range. For this signal, the
most common output impedance is 50 . However, sometimes lower output
impedance could be found.
ii. The arbitrary output or sometimes called “sync” or “TTL” signal. This signal
produces a standard square wave with 0 and 5 volt digital signal levels. This signal is
useful for synchronizing another device i.e., an oscilloscope to the possibly variable
main output signal.
Fig. H – Outlets of a function generator for the output signals
Oscilloscope
An oscilloscope (shown in Fig. I(a)) is a type of signal analyzer. It displays the measured
or collected signal being explored in the experiment in the form of a voltage versus time
graph. The user can then study this displayed output to learn the required electrical
properties such as the amplitude, frequency, and overall shape of the signal. The signal
from the circuit is measured using a probe (shown in Fig.I (b)). Signal displayed on the
oscilloscope is actually the potential difference between the two terminals of the probe.
The probe’s terminal ending with a hook is connected to the point in the circuit whose
voltage is of interest while the other terminal is usually (but not always) connected to the
ground. The other end of the probe is attached to input channels of the oscilloscope.
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Fig. I – Oscilloscope and its probe
Most modern oscilloscopes will have at least two input channels. Multiple channels are
useful for comparing waveforms. For instance, the user can observe both waveforms at
the input and the output terminals of a circuit simultaneously, by using a two-channel
oscilloscope.
Measurement Techniques
Oscilloscope is used mainly to observe a signal on the oscilloscope screen and make
voltage and time measurements. These measurements are useful in understanding the
behaviors of electronics device, or the circuit itself. The oscilloscope displays the voltage
value of the waveform as a function of time. The oscilloscope screen is partitioned into
the grids as shown in Fig. J, which divides both the horizontal axis (voltage) and the
vertical axis (time) into divisions.
Fig. J – Grids on an oscilloscope grid.
With a stable waveform, user can easily measure the frequency and the amplitude of the
waveform. Users have to know the time or the voltage values equivalent to each
division, in order to know the accurate measured values. These equivalent values are
determined by two variables namely the time/div and the volt/div which can be adjusted
as shown in Fig. K. Many modern oscilloscopes have the automatic measurement
function (auto-measure) which allows results to be displayed automatically on the screen
without user need to adjust the time/div or volt/div settings. However, the users need to
understand the basic measurement technique to obtain the most suitable waveform
displayed on the oscilloscope screen.
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Fig. K – Settings for volt/div and time/div
Amplitude measurement
Firstly, user has to estimate the number of divisions on the vertical scale from the peak to
the valley of the waveform. Next, multiply the number of divisions by the value of
volts/div to get the peak-to-peak voltage of the waveform. Users can adjust a couple
things to make the measurement easier. The volt/div can be adjusted so that the
waveform amplitude occupies a good portion of the vertical scale and does not go beyond
the limit of the vertical scale. Sometimes, the vertical position knob has to be adjusted too
to set the peak or valley of the waveform at the beginning of a division so that the
measurement so that the amplitude is more straightforward.
Frequency measurement
To measure frequency, user must estimate the number of divisions on the horizontal scale
for one complete period of a waveform. The number of divisions multiplied by the
time/div is the period of the waveform. Note that frequency is the reciprocal of the
period.
Phase measurement
In some applications, user may need to monitor or compare two or more signals
simultaneously. A typical example can be the comparison of the input voltage with the
output voltage of the input and output ports of the circuit. If the signals that are being
monitored have the same frequency, a time delay may occur between the signals.
Two waves that have the same frequency, have a phase difference that is constant or
independent of t. The waves are said to be in phase with each other. Otherwise, the waves
are out of phase with each other. If the phase difference is 180 degrees in radians, then
the two signals are said to be in anti-phase. To check the anti-phase condition is by their
summing the peak amplitudes of two anti-phase waves and the result should be zero at all
values of time.
- 20 -
EXPERIMENT 1:
Ohm’s Law & Series and Parallel
Circuits
Objectives:
a) To verify Ohm’s law (V=IR) where current through a resistor is proportional to
the voltage across it.
b) To verify that in a series circuit;
 The total resistance is equal to the sum of the individual resistors.
 The voltage drops across the resistors equals to the applied voltage.
 The value of the current is the same in all parts of the circuit.
c) To verify that in parallel circuits;
 The equivalent resistance is the reciprocal of the sum of reciprocals of the
individual resistors.
 The branch current in parallel equal to the supply current.
 The voltage drop across each resistor in parallel is the same.
 To verify by measurement and calculation for two different networks: the
total current and the branch values, the voltage drop across various parts of
the networks and the method for determining the equivalent resistance of
such networks.
Equipment:
Instruments
DC power supply
Two digital multimeters.
Components
Resistors ; 1.0kΩ, 1.5kΩ, 6.8kΩ
Procedures:
Part A : Ohm’s Law
1. Connect the circuit shown in Fig. 1.1.
2. Measure the actual value of each resistor and record in Table 1.1
3. Beginning at 0 V, increase the voltage across R3 in 1-Volt steps until 6 V.
Measure and record the resulting current in Table 1.1 for each increment of
voltage.
4. Plot the graphs of I verses V for results in Table 1.1. (Assign I to the vertical axis
and V to the horizontal axis).
5. Construct a right triangle on the graph and from this, re-determine the slope and
hence evaluate the conductance, G.
6. From this information, evaluate the resistance, R. Record G and R for the graph in
the appropriate column in Table 1.2.
7. Compare these experimentally obtained values with those measured values
recorded in the respective tables.
- 21 -
Fig. 1.1
Part B : Series Circuits
1. Remove the voltmeter and ammeter connections from the circuit of Fig. 1.1.
2. Adjust the supply voltage (Vs) to 15V. (Note the value must be kept constant
throughout the test by connecting voltmeter across the voltage supply in the
circuit to observe the voltage.)
3. Switch off the supply. Connect the ammeter in position A.
4. Switch on the supply. Read the current through resistor R1.
5. Connect the voltmeter across R1 and measure the voltage drop across it.
6. Repeat 3 until 5 for the ammeter positions B, C, and D and the voltmeter
positions across resistors R2 and R3.
7. Record the voltage for close and open loop. Fill up the measured values in
Table 1.3
Part C : Parallel Circuits
1. Connect the circuit shown in Fig 1.2
2. Adjust the supply voltage 15V. (Note the value of the supply voltage and keep it
constant throughout the test.)
3. Switch off the supply. Connect the ammeter in position A, the total current, ITotal.
4. Switch on the supply. Measure voltage across resistor R1
5. Place the ammeter at positions B, C, and D and the voltmeter positions across
resistors R2 and R3. Be careful not to touch R3 during measurement, as it might be
hot.
6. Fill up the measured values in Table 1.4.
- 22 -
Fig 1.2
Part D: Analysis, deductions and conclusions:
1. Has Ohm’s law been verified?
2. What are the facts supporting this decision?
3. State the factors affecting resistance of a material with a uniform cross-sectional
area?
4. What are the common types of fixed and variable resistors? State usage of each
type.
5. If the resistor from the experiment above is changed to 10 kΩ, deduct what will
happen to the slope of I-V graph. What effect on the conductance G?
6. Do all resistors obey Ohm’s law? Justify your answer by stating some examples.
7. Have each point in aims (b) and (c) been achieved?
8. What are the facts supporting these decision for each point of the aims (b) and
(c)?
9. What are the probable factors, which contributed to the discrepancies in the
results for each point of the aims (b) and (c)?
10. Indicate which circuit the principle of voltage division and current division is
applicable to.
11. State the formula for each condition.
- 23 -
Results and Calculations:
Table 1.1
R = 6.8kΩ
Measured Resistance, R =
R = 1 kΩ
Measured Resistance, R =
R = 1.5 kΩ
Voltage Source
(Vs)
Current
(Measured values)
Current
(Theoretical values)
Measured Resistance, R =
(V)
0
1
2
3
4
5
6
(mA)
(mA)
Table 1.2
Slope (G)
R (1/G)
Measured Values
Theoretical Values
Table 1.3
Supply voltage
(volt)
V1
(volts)
V2
(volts)
V3
(volts)
Σ Voltage
(volts)
Supply current
(mA)
I1
(mA)
I2
(mA)
I3
(mA)
I Total
(mA)
Total resistance
(Ohms)
R1
(Ohms)
R2
(Ohms)
R3
(Ohms)
ΣR
R1+R2+R3
Table 1.4
Supply current
(ampere)
I1
(amperes)
I2
(amperes)
I3
(amperes)
Supply voltage
(volt)
V1
(volts)
V2
(volts)
V3
(volts)
Equivalent
resistance
R1
(Ohms)
R2
(Ohms)
R3
(Ohms)
Equivalent
resistance
Total conductance
G1
(Siemens)
G2
(siemens)
G3
(siemens)
ΣG
- 24 -
Σ Current
EXPERIMENT 2:
Kirchhoff’s Voltage and Current Laws
Objective:
a) To verify Kirchhoff’s voltage and current laws.
Equipment:
Instruments
DC power supply
Three digital multimeters.
Components
Resistors ; 300Ω (2), 330 Ω, 1.8 kΩ, 2.7 kΩ, 3.0 kΩ
Procedures:
Part A: Kirchhoff’s Voltage Law:
1. Measure the resistance of each resistor. Set the supply voltage to 10 V. Record
the measured values in Table 2.1.
2. Construct the circuit shown in Fig. 2.1
3. Commence at point A and measure the potential difference between each
successive pair of lettered terminals for Mesh 1. i. e. A-B, B-C, C-D and D-A.
(Note: DMM’s probes have to be placed consistently.)
4. Record down the measured values in Table 2.2.
5. Measure the potential difference for the points AC, CE and EA. Verify
Kirchhoff’s voltage law using the displayed values. (Note that VCA is actually
VC – VA). What can be deduced from this condition? Record the measured
values in Table 2.3.
Fig. 2.1
- 25 -
Part B: Kirchhoff’s Current Law:
1. Measure the branch currents entering node A by placing ammeter as shown in
Fig. 2.1.
2. Record the magnitude and the direction of the current as indicated by each
ammeter in Table 2.4.
Part C: Analysis, deductions and conclusions:
1. Has Kirchhoff’s laws been verified? What facts determined for the results of
this test support this decision?
2. Are there any circuit configurations for which Kirchhoff’s laws are not
applicable?
Substantiate your answer.
3. For what type of circuit configurations would it be prudent not to apply
Kirchhoff’s laws?
- 26 -
Results and Calculations:
Measured components values
Table 2.1
V1
R1
R2
R3
R4
R5
R6
Table 2.2
Reference
points
Measured Values
Potential
Difference (V)
Sign (+ or -)
Theoretical Values
Potential
Difference (V)
Sign (+ or -)
A-B
B-C
C-D
D-A
Table 2.3
Reference
points
Measured Values
Potential Difference
(V)
Sign (+ or -)
Theoretical Values
Potential
Difference (V)
A-C
C-E
E-A
Table 2.4
Resistance
Current
Current direction
R3
R4
R6
- 27 -
Sign (+ or -)
EXPERIMENT 3:
Verification of Superposition Theorem
Objective:
a) To verify experimentally the Superposition theorem which is an analytical
technique of determining currents in a circuit with more than one EMF source.
Equipment:
Instruments
Two DC power supplies of suitable voltage and current ratings.
Three DC voltmeters (0-5 V).
One multimeter.
Trainer board
Components
Three potentiometers (10 k)
Procedures:
1. Set up the network (circuit) as in Fig. 3.1.
2. Apply 5 volts from E1 and 10 V from E2.
3. Use the DMM to measure the resistance
i. Set potentiometer 1 to 1 kΩ
ii. Set potentiometer 2 to 2 kΩ
iii. Set potentiometer 3 to 3 kΩ
4. Measure the current I2 and record it in Table 3.1.
5. Render E2 inactive.
6. Measure the current I2’ in the branch R2 and record it in Table 3.1.
7. Render E1 inactive.
8. Measure the current I2’’ in the branch R2 and record it in Table 3.1.
9. Verify if I2 = I2’ + I2’’ which would validate the superposition theorem for this
particular circuit.
10. Repeat steps 4 to 10 by rotating the positions of R1, R2, and R3 and take two more
sets of readings
11. Find theoretically the current I2 with reference to Fig. 3.1 by applying the
superposition theorem considering E1 = 15 volts, E2 = 20 volts and R1, R2, R3 at
1 kΩ, 2 kΩ and 3 kΩ respectively.
S2 1
1 S1
2
R1
S3
E1
A
R2
I2
Fig. 3.1
- 28 -
R3
2
E2
Results and Calculations:
Table 3.1
Values of resistors (ohms)
R1
R2
I2 with both E1 and E2
active (amps)
R3
- 29 -
I2’ with only E1 active
(amps)
I2’’ with only E2 active
(amps)
EXPERIMENT 4: Thevenin’s & Norton’s Theorem and
Maximum Power Transfer Theorem
Objectives:
a) To applied Thevenin’s and Norton’s theorems in finding the current
flowing in a particular resistor (variable load) in a particular network.
b) To verify the theorems by comparing the simulated values to those
obtained by measurement.
c) To verify the maximum power transfer theorem.
Equipment:
Instruments
DC power supply
Digital multimeters
Components
Resistors 1.8kΩ; 3.6kΩ; 820Ω; 100 Ω (2); 180 Ω
Rheostat (2)
Procedures:
Part A – Thevenin’s Theorem
1. Measure the resistance of each resistor. Record these values in Table 4.1 Select
RL as the resistor where it is proposed to determine the current value.
2. Construct the circuit in Fig 4.1.
3. Remove resistor RL from the network.
4. Turn on the supply and set the power supply to 10 V. Measure the voltage
between the points A and D of the network. This is the Thevenin’s voltage.
Record the value in Table 4.2
5. Switch off the power supply. Replace the power supply V1 with a short circuit.
6. Measure the resistance between terminals A and D. This is the Thevenin’s
resistance. Record the value in Table 4.2
7. Place back the resistor RL in circuit with an ammeter is connected between
terminals A and B or C and D.
8. Remove the short circuit connection and place back the supply in the circuit.
9. Turn on the supply. Read and record the current value flowing in the resistor
RL.
10. Draw Thevenin’s equivalent circuit inclusive of resistor RL.
- 30 -
Fig. 4.1
Part B – Norton’s Theorem
1. Construct the circuit as shown in Fig. 4.1. Do not turn on the supply
2. Remove resistor RL from the network. RL is selected as the resistor where it is
proposed to determine the current value.
3. Turn on the supply. Read the current shown by the ammeter between terminals
A and D. This is Norton’s current, IN. Record its value in Table 4.3.
4. Switch off the power supply. Replace the supply with a short circuit.
5. Measure the resistance between terminals A and D. This is Norton’s
resistance, record the value in Table 4.3.
6. Place back the resistance RL in circuit with an ammeter is connected between
terminals A and B or C and D.
7. Place back the power supply in the circuit and remove the short circuit
connection.
8. Read and record the current value flowing in the resistor RL.
9. Draw Norton’s equivalent circuit inclusive of resistor RL.
Part C– Maximum Power Transfer
1. Set up the circuit as shown in Fig. 4.2.
IL
Fig. 4.2
2. Set Vth as 10 V from the DC power supply.
3. Use the resistor, Rth = 5 kΩ
- 31 -
4.
5.
6.
7.
Vary the load rheostat RL from 0 Ω to 10 kΩ.
Measure the voltages VL and I. Take 11 sets of reading.
Record all result in Table 4.4.
Plot the following curves on the graph paper and attach them to your report:
(i) % η vs RL
(ii) % VR vs RL
(iii) loss vs RL
(iv) POUT vs RL
(v) IL vs RL
(vi) VL vs RL
Part D– Analysis, deductions and conclusions
1. What facts deduced from the results of this test indicate whether the theorems
have been verified or not?
2. Is Thevenin’s theorem is likely to be widely used in practice?
3. Is the fact that the Norton’s theorem is based on the concept of a constant
current generator likely to limit its usage? Why?
4. What type of problems each theorem is most applicable in the circuit analysis?
5. Are the theorems valid if there is more than one supply in the circuit? Give your
reasons.
6. Are the theorems applicable with presence of dependent sources in the
circuit? Give your reasons.
7. Has the maximum power transfer theorem been verified from the experiment?
What facts determined from the results support this decision?
8. Why high voltage transmission is used in case of transmitting electric power?
9. Where maximum power transfer is used?
10. Why instead of transmitting maximum power, power utility transmits power at
maximum efficiency?
11. Deduce the condition for maximum power transfer.
- 32 -
Results and Calculations:
Table 4.1
Measured values
V1
R1
R2
R3
R4
R5
RL
Table 4.2
Measured values
Thevenin’s
resistance
Thevenin’s
voltage
Theoretical values
Thevenin’s
resistance
current in
RL
Thevenin’s
voltage
current in
RL
Table 4.3
Measured values
Norton’s
Resistance
Norton’s
current
Theoretical values
Norton’s
resistance
current in
RL
Norton’s
current
current in
RL
Table 4.4
RL
(k)
VTH
VL
I
PIN = VTH I POUT = VL I Loss = PIN  POUT
0
1
2
3
4
5
10V
6
7
8
9
10
- 33 -
%η
%VR
EXPERIMENT 5:
Diode Characteristic and Application
Objectives:
a) To study the characteristics of a silicon (Si) diode and a germanium (Ge)
diode.
b) To calculate and draw the DC output voltages of half-wave
Equipment:
Instruments
DC power supply
2 Digital Multimeters (DMM)
Function Generator
Oscilloscope
Components
Silicon Diode (D1N4002), Germanium Diode (1N34A)
Resistors: 1kΩ
Resistors: 2.2kΩ, 3.3kΩ
Procedures:
Part A : Forward-bias Diode Characteristics
1. Construct the circuit as is shown in Fig. 5.1 using a Si diode.
Fig. 5.1
2. By varying the DC Supply voltage, set the diode voltage VD = 0 V and measure
diode current ID and record the result in Table 5.1
3. Now, set the diode voltage VD = 0.1V. Measure the corresponding diode current
ID and record the result in Table 5.1
4. Repeat step 2 for the remaining settings of VD shown in the Table 5.1.
5. Replace the Si diode by a Ge diode and complete Table 5.2.
- 34 -
6. Plot ID versus VD characteristics curves on a graph paper for both silicon and
germanium diodes.
Part B : Half Wave Rectification
1. Construct the circuit of Fig. 5.2. Set the supply to 9 V p-p sinusoidal wave with
the frequency of 2 kHz. Put the oscilloscope probes at function generator and
sketch the input waveform obtained.
2. Put the oscilloscope probes across the resistor and sketch the output waveform
obtained. Measure and record the DC level of the output voltage using the DMM.
Fig. 5.2
3. Reverse the diode of circuit of Fig. 5.2. Sketch the output waveform across the
resistor. Measure and record the DC level of the output voltage.
4. Comment on the results obtained from step 2 and 3.
PSPICE Instructions:
Get the expected output waveform for circuits in Fig. 5.2 using PSPICE simulation.
- 35 -
Results and Calculations:
Part A – Diode Characteristics (Forward Bias)
Table 5.1 (Silicon Diode)
VD (V)
ID
(mA)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.75
0.6
0.7
0.75
Table 5.2 (Germanium Diode)
VD (V)
ID
(mA)
0
0.1
0.2
0.3
0.4
0.5
Part B – Half Wave Rectification
1. Input waveform, Vi :
V(volt)
Time (s)
2. Output waveform, Vo :
V(volt)
Time (s)
DC level of Vo (measured) = __________
- 36 -
EXPERIMENT 6:
BJT Characteristics & Biasing Circuits
Objectives:
a) To provide the characteristics of a transistor using experimental methods.
b) To determine the quiescent operating conditions of a voltage-divider-bias BJT
configurations.
Equipment:
Instruments
1 DC Power Supply
3 Digital Multimeter (DMM)
Components
Resistors: 680 , 6.8 k, 1 k, 3 k, 22 k, 330 k, 10 k potentiometer,
1M potentiometer
Transistors:
2N3904
Procedures:
Part A : The Collector Characteristics (BJT)*Using two potentiometers*
1. Construct the circuit of Fig. 6.1. Vary the 1M potentiometer to set
IB = 10 A as in Table 6.1.
Fig. 6.1
2. Set the VCE to 2V by varying the 10 k potentiometer as required by the first
line of Table 6.1.
3. Record the VRC and VBE values in Table 6.1.
4. Vary the 10 k potentiometer to increase VCE from 2V to the values
appearing in Table 6.1. (Note: IB should be maintained at 10 A for the range
of VCE levels.)
- 37 -
5. Record VRC and VBE values for each of the measured VCE values. Use the mV
range for VBE.
6. Repeat step 2 through 5 for all values of IB indicated in Table 6.1.
7. Compute the values of IC (from IC = VRC/RC) and IE (from IE = IB+IC). Use
measured resistor value for RC.
8. Using the data of Table 6.1, plot the collector characteristics of the transistor
on a graph paper. (Plot IC versus VCE for the various values of IB. Choose an
appropriate scale for IC and label each IB curve).
Part B : Voltage-Divider-Bias Configuration
1.
2.
Measure all resistor values (R1, R2, RE and RC) from circuit in Fig. 6.2 using
DMM. Record them.
Construct the network of Fig. 6.2 and measure VB, VE, VC and VCE. Record them
in Table 6.2.
Fig. 6.2
3.
4.
5.
Measure the voltages VR1 and VR2. Calculate the currents I1 and I2 using Ohm’s
Law.
Using Kirchoff’s current law, calculate the current IB. Then, measure the currents
IE and IC values. Then complete Table 6.2.
Confirm that IB calculated using KCL is equal to the IE-IC
PSPICE Instructions:
Using PSPICE Simulation, find the values of VB, VE, VC, VCE, IC, IB and IE for the circuit
in Fig. 6.2. Compare the values obtained from PSPICE with the experimental ones.
- 38 -
Results and Calculations:
Part A – The Collector Characteristics
Table 6.1
IB
(A)
10
VCE
(V)
meas
2
VRC
(V)
meas
IC
(mA)
(calc)
VBE
(V)
meas
4
6
8
2
30
4
6
8
2
50
4
6
8
Part B – Voltage Divider Biasing
R1 (measured) = ____________, R2 (measured) = ___________,
RC (measured) = ___________, RE (measured) = ___________
I1 = _______________, I2 = ________________
Using KCL, IB = _______________
Table 6.2
VB(V) VE(V) VC(V) VCE(V) IE(mA) IC(mA)
Measured (Step 3&4)
- 39 -
IE
(mA)
(calc)
EXPERIMENT 7:
MOSFET – Common-Source Amplifier
Objective:
a) To perform the DC and AC analyses of a common source amplifier using an
n-channel MOSFET.
Equipment:
Instruments
DC power supply
Function Generator
Digital Multimeter (DMM)
Oscilloscope
Components
NMOS: 2N 7000
Resistors: 6.8 kΩ, 33 kΩ, 100 Ω, 3.3 kΩ, 2.7 kΩ
Capacitors: 1 µF
Procedures:
Part A : MOSFET DC Analysis
1. Construct the circuit of Fig. 7.1 but DO NOT CONNECT the capacitor yet
and record the measured values of the resistors.
Fig. 7.1
2. Using the DMM, measure the values of VGS, VDS and ID.
- 40 -
3. Using the threshold voltage, VTN = 2.1 V, please confirm that the transistor is
in saturation. (VDS > VDSsat and VDSsat = VGS - VTN)
4. From the measured value of ID, deduce the value of the conduction parameter
Kn using the drain current in saturation formula
Part B : Common Source Amplifier (AC Analysis)
1. By using the same circuit configuration – connecting the capacitor this time,
set the function generator to 100 mV amplitude, 20 kHz sinusoidal wave.
Connect it to vin.
2. Connect Channel 1 of the oscilloscope to vin and Channel 2 of the oscilloscope
to vout.
3. Measure the peak-to-peak value for both input and output voltages on Channel
2 of the oscilloscope.
4. Calculate the value of the gain, vo / vi
PSPICE Instructions:
1. Construct the circuit in Figure 8.1 using PSPICE.
2. From PSPICE simulation, obtain the DC voltages at all terminals of
MOSFET, VGS, VG and VDS.
NOTE:
Unfortunately, this transistor model is not in the default library. Hence, you have to add
the 2N7000 model if you would like to use it in PSPICE.
Go to the Breakout Library  Choose MBreakN3  Placed it in your circuit
Select the transistor  Go to Edit  PSpice Model
A Model Editor window will appear. Paste the TEXT file below and click Save.
The Text File
.MODEL 2N7000 NMOS (LEVEL=3 RS=0.205 NSUB=1.0E15 DELTA=0.1
+KAPPA=0.0506 TPG=1 CGDO=3.1716E-9 RD=0.239 VTO=2.100 VMAX=1.0E7
+ETA=0.0223089 NFS=6.6E10 TOX=1.0E-7 LD=1.698E-9 UO=862.425
+XJ=6.4666E-7 THETA=1.0E-5 CGSO=9.09E-9 L=2.5E-6 W=0.8E-2)
- 41 -
Results and Calculations:
Part A (MOSFET - DC Analysis)
1. R1 (measured) = _______________
RA (measured) = _______________
RB (measured) = ________________
RD (measured) = _________________
Rs (measured) = _________________
2. VGS (measured) = _______________, VDS (measured) = ______________ and
ID (measured) = ________________
3.
Confirmation that the transistor is in saturation:
4. Conduction parameter, Kn = ___________
Part B (MOSFET-AC Analysis)
vin (peak-to peak) = __________
vout (peak-to peak) = ___________
Gain = __________________
- 42 -
EXPERIMENT 8:
Inverting and Non-inverting Op-Amp
Objectives:
a) To observe the basic Op-amp circuits characteristic as inverting and noninverting amplifiers.
b) To build and test Op-amp application circuits - inverting and non-inverting
amplifier
c) To observe the virtual ground and the input resistance of the amplifiers
Equipment:
Instruments
 DC power supplies – You need two power supplies. One for 15V and
another one for the -15V
 Digital Multimeter (DMM)
 Function Generator
 Oscilloscope
Components



Op Amp : LM 741
Resistors: 1 k, 20 k, 30 k, 10 k, 100 k
Capacitor: 0.1 F
Procedures:
Part A: Inverting Amp
1. Set up the oscilloscope to show a dual trace, one for the input of the op-amp and
one for the output. Use DC input coupling. Set up the function generator to
produce a sine wave with an amplitude of 1 V peak-to-peak and frequency 2 kHz.
Make sure that the grounds of the function generator, oscilloscope, and
prototyping board are somehow connected.
2. Measure the values of the resistors, then using the breadboard, set up the inverting
amplifier shown in Fig. 8.1 where R1 = 10 k and RF = 100 k
3. Measure the voltage between pin 2 and ground. This is known as virtual ground.
Record the voltage and comment on your observation.
4. From the output waveform, deduce the gain of the amplifier and verify that the
amplifier inverts.
5. Next, repeat step 4 by replacing R1 with the 30 k and 20 k resistors
6. Using the measured values of the resistors, calculate the ratio of RF/R1 and
compare whether the magnitudes are equal to the magnitude of the gain that have
been deduced from step 4.
7. Using R1 as 20 k, now place a load resistor, RL = 1 k between pin 6 and the ground.
Repeat step 4. Comment on your observation. Is there any change in the value of the
gain?
- 43 -
Fig. 8.1 – Inverting Amplifier
Part B: Non-Inverting Amp
1. Construct the non-inverting amplifier as shown in Fig. 8.2. Use RF = 10 k and
R1= 1 k
2. Apply a 2 kHz sinusoidal input signal with 1 V peak-to-peak amplitude, to the
amplifier. Display vin and vout at the same time. (They need to be displayed
simultaneously so that you can see the phase shift between them.)
3. Sketch the input and output waveforms on the same time scale.
4. Report the phase shift and deduce the gain of the amplifier
5. Using the measured values of the resistors, calculate the value of (1+ RF/R1) and
compare whether the magnitude is equal to the magnitude of the gain that have
been deduced from step 4.
6. Measure the voltage between pin 2 and ground. Discuss your observation with
respect to step 3 from Part A (inverting).
7. Now place a resistor, R = 20 k, between pin vin and pin 3. Repeat step 4.
Comment on your observation. Is there any change in the value of the gain?
Fig. 8.2 – Non-Inverting Amplifier
PSPICE instruction:
- Construct both circuits and obtain the input-output waveform for both of the
inverting and non-inverting op-amp.
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Results and Discussions:
Part A (Inverting Amplifier) :
1. a) R1k ( measured ) = _______________
b) R10k ( measured ) = ________________
c) R20k ( measured ) = ________________
d) R30k ( measured ) = ________________
e) R100k ( measured ) = ________________
2. Voltage measurement between pin 2 and ground = _________________
3. Gain of the amplifier = vo (peak) / vi (peak) = _______________
4. a) When R1 = 30 k : Gain of the amplifier = vo (peak) / vi (peak) = ______________
b) When R1 = 20 k : Gain of the amplifier = vo (peak) / vi (peak) = ______________
5. Ratio of RF/R1
R1 = 10 k : RF/R1 = _______________________
R1 = 30 k : RF/R1 = _______________________
R1 = 20 k : RF/R1 = _______________________
Comment of the comparison between the magnitudes:
6. With load resistor, RL = 1 k, gain of the amplifier = ________________
Comment:
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Part B (Non-Inverting Amplifier) :
1. Input and Output waveform on the same time scale
2. a) Phase shift, Ф = ___________
b) Gain of the amplifier = vo (peak) / vi (peak) = _______________
3. Value of (1+ RF/R1 ) = _______________________
Comment of the comparison between the magnitudes:
4. Voltage measurement between pin 2 and ground = _________________
Comment in comparison with step 3 from Part A
5. With resistor, R = 20 k between vin and pin 3, gain of the amplifier = ________
Comment:
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