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FACULTY OF ENGINEERING AND INFORMATION TECHNOLOGY

DEPARTMENT: Electrical, Electronic, and Computer Engineering

MODULE NAME: Electronics II

MODULE CODE: EEL125C

NQF LEVEL: 7

CREDITS: 14

COMPILED BY: Prof ED Markus & T Mokhali

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Table of Contents
ELECTRONIC II (EEL125C) LABORATORY EXPERIMENTS .............................................................. 3

Assessment Components and due dates ......................................................................................................... 3

Laboratory Practical ...................................................................................................................................... 4

Oscilloscope and Function Generator Operation .......................................................................................... 5

EXPERIMENT 1: BJT Characteristics ....................................................................................................... 10

EXPERIMENT 2: Operational Amplifiers ................................................................................................. 17

EXPERIMENT 3: Oscillator Circuits (The phase – Shift Oscillator) ......................................................... 22

EXPERIMENT 4: frequency response of common-emitter amplifiers....................................................... 25

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ELECTRONIC II (EEL125C) LABORATORY EXPERIMENTS

Assessment Components and due dates

Assessment Topic Weight Date

Instrument (%)

Tutorial Oscilloscope & Function 0

Generator Function
Experiment 1 (E1) BJT Characteristics 20 11 Aug – 15 Aug
(due 17 Aug)
Experiment 2 (E2) Linear OP-amp circuits 15 18 Aug – 22 Aug
(due 24 Aug)

Experiment 3 (E3) Signal generators 15 25 Sept – 29 Sept

(due 31 Aug)
Experiment 4 (E4) Frequency response 0

Practical Mark (PM) 35% 4 Oct

2025_Practical Mark = (33% X 2025_E1 Mark) + (33% X 2025_E2 Mark) + (34% X 2025_E3 Mark)

Please, note the following for the specific assessment components:

• The provided dates are tentative and may change during the semester.
• LI File submissions: Only TWO attempts.
• Answer all questions and enter your answers on ETHUTO on the spaces provided: Only SINGLE
attempt.
• Please, take note of the format and / or notation in which the answers are required. In addition,

.
Ethuto/Blackboard uses a dot ( ) instead of a comma (,).
• Round all answers to two (2) decimal places with calculator in the engineering mode.
• All the screenshots MUST include a student number, time and date.
• No answers will be marked when submitted beyond the allocated time.
• NO E-MAILED ANSWERS/SOLUTIONS WILL BE ACCEPTED.
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Laboratory Practical

Laboratory name

Assessor name and Signature:

Assessment date:

Student initials and surname:

Student number:

DECLARATION OF OWN WORK

I ………………………………………………………………………………………………….
hereby declare that this is my own work and that it has not been copied from any other person or
document.

………………………………………… …………………………..

Signature Date
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Oscilloscope and Function Generator Operation

Objective:

1. Learn how to operate a function generator.

2. Learn how to use an oscilloscope to visualize signals.
3. Understand how both devices work together in signal analysis.
4. Observe and interpret waveforms (sine, square, triangle).

Resume of Theory:

Figure 1: Oscilloscope

Oscilloscope
The oscilloscope is the most important instrument available to the practicing technician or
engineer. It permits the visual display of a voltage signal that can reveal a range of information
regarding the operating characteristics of a circuit or system that is not available with a standard
multimeter (DMM). At first glance the instrument might seem complex and difficult to master.
But one the function of each section is explained and understood and used with the prescribed
experiments, your expertise will develop steadily.

In addition to the display of a signal, it can also be used to measure the average value, rms
value, frequency and period of sinusoidal or non-sinusoidal signal. The screen is divided into
centimetres divisions in the vertical and horizontal directions. The vertical sensitivity is
provided in volts/div and the horizontal sensitivity is provided in t time (sec/div).
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Function Generator
The function generator is a voltage supply that provides a sinusoidal, square-wave, and
triangular voltage waveform for a range of frequencies and amplitudes. Although the frequency
of the function generator can be set by the dial position and appropriate multiplier, the
oscilloscope can be used to precisely set the output frequency. The scope can also be used to
set the amplitude of the function generator since most function generators simply

Figure 2: Function generator

Part 1: Setup
A. Turn on the oscilloscope and adjust the necessary controls to establish a clear,
horizontal line across the centre of the screen. Do not be afraid to adjust the various
controls to see their effects on the display.

B. Connect the function generator to channel 1 of the oscilloscope and set the output of
the generator to a 1000 Hz sinusoidal (sine) waveform.

C. Press the MEASURE button found on the front panel of the oscilloscope to set the
parameters you will measure.

D. Press the top option button next to the screen and set the source to CH1 and Type to Pk-

Pk. Press the back button

E. Repeat steps c to e to display Freq, Period, mean, and RMS with the other option
buttons.

F. Adjust the amplitude control of the function generator to establish a 4V peak-to-peak

(p-p) sine wave on the screen and record the following:
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Vpk-pk(measured) =

Frequency(measured) =

Period(measured) =

Mean(measured) =

RMS (measured) =

Part 2: Vertical Sensitivity

a. Adjust the vertical sensitivity (volt/div) of the oscilloscope up and down and observe what
happens to the sine wave.

What was the effect on the sine wave when the volt/div was increased?

What was the effect on the sine wave when the volt/div was decreased?

Part 3: Horizontal Sensitivity

a. Adjust the horizontal sensitivity (sec/div) of the oscilloscope up and down and observe what
happens to the sine wave.

What was the effect on the sine wave when the sec/div was increased?

What was the effect on the sine wave when the sec/div was decreased?
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Part 4: Exercise
a. Make all the necessary adjustments to display a 5000 Hz, 4V peak-to-peak (p-p) sine wave
on the oscilloscope and record the following:

Vpk-pk(measured) =

Frequency(measured) =

Period(measured) =

Mean(measured) =

RMS (measured) =

Part 5: The Effect of DC levels

a. Disconnect the function generator from the scope and measure the effective (rms) value
of the output of the function generator using the digital multimeter (DMM). Set the DMM
to AC.

RMS(DMM) =

b. Determine the magnitude of the percentage difference between the Vrms (oscilloscope)
and Vrms (DMM) using the following equation.

𝑉𝑟𝑚𝑠(𝑜𝑠𝑐) − 𝑉𝑟𝑚𝑠(𝐷𝑀𝑀)
%𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 100%

%Difference =

c. Reconnect the function generator to the oscilloscope and set the coupling option to GND.
What is the effect?
Why?

d. Now set the coupling to AC. What is the effect on the display? Why?

e. Lastly, set the coupling to DC. What is the effect? Why?

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Part 6: The Effect of Probe attenuation

a. Set the probe attenuation to 10X. What is the effect?

b. Set the probe attenuation to 1X. What is the effect?

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EXPERIMENT 1: BJT Characteristics

Objective:

To determine transistor type, terminals and material using the multimeter (DMM).
To plot the collector characteristics of a transistor. To
determine the value of the beta ratio of a transistor
Assessment Criteria based on Ethuto:

2025_E1 Mark

20% 2025 Experiment 1: BJTs VRB = 3.3V (Screenshot)

Mark allocation (6):

Correct simulation screenshot of the schematic as seen in Figure 4. (1) (Screenshot required)

Student surname and student number on the simulator. (1)

Correct value of VRB. (2)

Correct value of IB. (2)

20% 2025 Experiment 1: BJTs VCE = 2V (Screenshot)

Mark allocation (5):

Correct picture of the output waveform required (4)

Scan the signed experiment document and include a display of your student card next to the scope. (1)
(Screenshot required)

30% 2025 Experiment 1: BJTs Collector characteristics plot (picture)

Mark allocation (10):

Correct and completed

Table 3. (6)

Correct collector characteristics of the transistor graph. (3) (Picture of the graph required)

Student surname and student number on the simulator. (1)

30% 2025 Experiment 1: Determination of the transistor type, Terminals and Material (Answers on Ethuto)
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Reading: Chapter: Boylestad, R. L. & Nashelsky, L. 2013. Electronic Devices and Circuit
Theory (11th Edition). United States of America: Prentice-Hall, Inc.).
Resume of Theory: BJTs operate in three modes: cut-off, saturation, and linear. In each of
these modes, the physical characteristics of the transistor and the external circuit connected to
it uniquely specify the operating point of the transistor. In the cut-off mode, there is only a
small amount of reverse current from emitter to collector, making the transistor akin to an open
switch. In the saturation mode, there is a maximum current flow from collector to emitter. The
amount of that current is limited primarily by the external network connected to the transistor;
its operation is analogous to that of a closed switch. Both of these operating modes are used in
digital circuits.

For amplification with a minimum of distortion the linear region of the transistor characteristics
is employed. A DC voltage is applied to the transistor, forward-biasing the base-emitter
junction and reverse-biasing the basecollector junction, typically establishing a quiescent point
near or at the centre of the linear region.

In this experiment, we will investigate the voltage-divider bias configuration. The voltage-
divider bias network employs a feedback arrangement that makes the base-emitter and
collector-emitter voltages primarily dependent on the external circuit elements and not the beta
of the transistor. Thus, even though the beta o individual transistors may vary considerably, the
location of the Q-point on the load line will remain essentially fixed. The phrase “beta-
independent biasing” is often used for such an arrangement.

How to submit:
a. Present your results on a neat printed practical guide during demonstration clearly
indicating you initials, surname and student number for signature on each page. Also,
present page 4 for signature when you’ve completed the experiment.

b. You are required to take a photograph (or scan) of your signed results.

c. You must paste the photos on a word document and save your photo using the following
file name: 2025_EEL125C_Exp num_StudentNumber_StudentSurname. Save the file
as .pdf for submittal.

d. Upload to eThuto via the Assignment under the Practical Work folder.

Part 1: Determination of the transistor type, Terminals and Material

Figure 3: Transistor
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a. Set the DMM to diode mode

b. Connect the positive lead of the DMM to terminal 1 and the negative to terminal 2. Record
in and complete the table.

Table 1
DMM leads Diode Mode

Positive lead Negative lead DMM reading

1 2

2 1

1 3

3 1

2 3

3 2

c. The DMM reading between two of the terminals will read high (O.L or higher resistance)
regardless of the polarity of the leads connected. Neither of these two terminals will be the
base. Based on the above, record the number of the base terminal in Table 2.

Table 2
Base terminal
Transistor type
Collector terminal
Emitter terminal
Transistor material

d. Connect the negative terminal to the base and the positive lead to any of the other terminals.
If the reading is

e. high, the transistor type is NPN. Record the transistor type in Table 2.

f. Connect the positive lead to the base terminal and the negative lead to the other two
terminals alternately. The lower of the two readings indicates that the base and collector are
connected, as such the other terminal is the emitter. Record the terminals in Table 2.

g. If the readings in the previous step were approximately 700 mV, the transistor material is
silicon. If the readings were approximately 300 mV, the transistor material is germanium.
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Part 2: Collector Characteristics

a. Construct the network in Figure 4

b. Set the voltage VRB to 3.3 V by varying the 1 MΩ potentiometer. This will set 𝐼𝐵 = 𝑉𝑅𝐵/𝑅𝐵
to 10µA as indicated in Table 3.
c. Then set 𝑉𝐶𝐸 to 2 V by varying the 5 KΩ potentiometer.
d. Record 𝑉𝑅𝐶 and 𝑉𝐵𝐸.
e. Vary the 5 KΩ potentiometer to increase 𝑉𝐶𝐸 from 2 V to the values appearing in Table 3.
f. For each value of 𝑉𝐶𝐸 measure and record 𝑉𝑅𝐶 and 𝑉𝐵𝐸.
g. Repeat step b to for all values of 𝑉𝑅𝐵 indicated in Table 3.
h. When all the data have been obtained, calculate the corresponding 𝐼𝐶 and 𝐼𝐸 values using
𝐼𝐶 = 𝑉𝑅𝐶/𝑅𝐶 and 𝐼𝐸 = 𝐼𝐶 + 𝐼𝐵. Use the measured value for 𝑅𝐶
i. Using the data of Table 3
j. Plot the collector characteristics of the transistor on Figure 5

Figure 4
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STUDENT NUMBER: _______________________

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Figure 5: Collector characteristics

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Experiment 1 – Equipment required (students may write the equipment serial numbers next to each equipment
used for later reference)

DC power Supply
DMM

Experiment 1 – Components Needed

Resistors:
One (1) 680 Ω
One (1) 1.8 kΩ
One (1) 6.8 kΩ
One (1) 33 kΩ

Transistors:
One (1) 2N3904 or equivalent
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EXPERIMENT 2: Operational Amplifiers

Objective:

To measure DC and AC voltages in the linear op-amp circuits. To

compute voltage gains of the various op-amps.

Assessment Criteria based on Ethuto:

2025 E3 Mark

56% 2025 Experiment 2: Inverting and non-inverting amplifiers (Answers)

22% 2025 Experiment 2: Non-inverting amplifier (Screenshot)

Mark allocation (5):

Correct picture of the output waveform required (4)

Scan the signed experiment doc and include a display of your student card next to the scope.
(1) (Screenshot required)

22% 2025 Experiment 2: Inverting Amp (Screenshot)

Mark allocation (5):

Correct picture of the output waveform required (4)

Scan the signed experiment document and include a display of your student card next to the
scope. (1) (Screenshot required)

Resume of theory:
The op-amp is a very high gain amplifier with inverting and noninverting inputs. It can be used to provide a much
smaller but exact gain set by external resistors or to sum more than one input causing a desired voltage gain.

As an inverting amplifier, the resisters are connected to the inverting input as shown in Figure 6 with output
voltage.

𝑅𝑜
𝑉𝑜 = − 𝑉𝑖
𝑖
Ro

Ri
Vi -
Vo
OUT

𝑅
Figure 6

A noninverting amplifier is provided by the circuit of Figure 7 with output voltage given by:
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𝑅𝑜
𝑉𝑜 = (1 + )𝑉𝑖
𝑖
Ro

Ri
-
Vo
OUT

+
Vi 𝑅
Figure 7

Connecting the output back to the inverting input as in Figure 8 provides a gain of exactly unity:

Vo = Vi

OUT Vo

+
Vi

Figure 8

More than one input must be connected through separate resistors as shown in Figure 9, with the output voltage
then:

𝑅𝑜 𝑅𝑜
𝑉𝑜 = −( 𝑉1 + )𝑉2
1 𝑅2
Ro
R2
V2

R1
V1 -
Vo
OUT

𝑅
Figure 9

How to submit:
a. Present your results on a neat printed practical guide during demonstration clearly indicating you initials,
surname and student number for signature on each page. Also, present page 4 for signature when you’ve
completed the experiment.

b. You are required to take a photograph (or scan) of your signed results.

c. You must paste the photos on a word document and save your photo using the following file name:
2025_EEL125C_Exp num_StudentNumber_StudentSurname. Save the file as .pdf for submittal

d. Upload to eThuto via the Assignment under the Practical Work folder.
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Part 1: Inverting Amplifier

a. Calculate the voltage gain for the amplifier of Figure 10 (Note: check the correctness of polarity pins 4 and
7)

𝑉𝑜/𝑉𝑖 (calculated) =………………………………

Ro

100k ohm

+V (+10 V)

4
Ri
Vi 2 1
- OS1
Vo
20k ohm 6
OUT

V+V-
3 5
+ OS2

-V (-10 V)

7
`
Figure 10

b. Construct the circuit of fig. (Measure and record resistor values in Figure 10) Apply an input of 𝑉𝑖 = 1 𝑉, rms
(f = 10 kHz). Using a DMM, measure and record the output voltage.

𝑉𝑜 (Measured) =……………………………

Calculate the voltage gain using measured values:

𝐴𝑣 =………………………………….

How does the gain calculated in step a. compare with that measured in step b.

c. Replace 𝑅𝑖 with a 100 k resistor. Calculate 𝑉𝑜/𝑉𝑖

𝑉𝑜/𝑉𝑖 (calculated) =………………………

For input of 𝑉𝑖 = 1 𝑉, rms measure and record 𝑉𝑜.

𝑉𝑜(Measured) =…………………………….

Calculate 𝐴𝑣.

𝐴𝑣 = ……………………………………..

How does the calculated gain compare with the measured gain.

d. Using the oscilloscope, measure the output waveform.

𝑉𝑜(𝑝𝑘−𝑝𝑘) =…………………………….

𝑉𝑜(𝑟𝑚𝑠) =……………………………….
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Part 2: Noninverting Amplifier

a. Calculate the voltage gain of the noninverting amplifier in Figure 11 (Note: check the correctness of polarity
pins 4 and 7)
+V (+10 V)

Vi 3 5
+ OS2
Vo
6
OUT
2 1
- OS1

R1 -V (-10 V)
20 k ohm
Ro

100 k ohm

Figure 11

𝐴𝑣 (Calculated) =………………………..

b. Construct the circuit of fig. (Measure and record resistor values in fig) Apply an input of 𝑉𝑖 = 1 𝑉, rms (f =
10 kHz). Using a DMM, measure and record the output voltage.

𝑉𝑜 (Measured) =…………………………

Calculate the voltage gain using measured values:

𝑉𝑜/𝑉𝑖 =………………………………..

How does the gain calculated in step a. compare with that measured in step b.

c. Replace 𝑅𝑖 with a 100 k resistor and repeat step a and b.

𝐴𝑣 (calculated) =…………………..

𝑉𝑜 (measured) =…………………….
𝑉𝑜/𝑉𝑖
=……………………..

How does the calculated gain compare with the measured gain.

d. Using the oscilloscope, measure the output waveform.

𝑉𝑜(𝑝𝑘−𝑝𝑘) =………………………..

𝑉𝑜(𝑟𝑚𝑠) =…………………………
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Experiment 2 – Equipment required (students may write the equipment serial numbers next to each equipment
used for later reference)

Oscilloscope
DMM
Function generator
DC power supply
Experiment 2 – Components Needed

Resistors
20kΩ 100kΩ ICs
741 op-amp
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EXPERIMENT 3: Oscillator Circuits (The phase – Shift Oscillator)

Objective:

To measure the amplitude, the frequency of Vout, and the open-loop gain of the op-amp as a phase-shift oscillator.
To compare these experimental results with their theoretical values.
If a deviation of more than 10% between these two sets of data is obtained, suggest and test a modification of the
circuit to bring the experimental results to within that deviation.

Assessment Criteria based on Ethuto:

2025 E4 Mark

60% 2025 Experiment 3: Phase-shift Oscillator (Answers)

40% 2025 Experiment 3: Phase-shift Oscillator (Lab completion)

Mark allocation (5):

Waveform with a visible student card (1)

Correct Vpeak to peak (2)

Correct frequency (2)

Resume of theory:
The circuit used in this experiment will exhibit sinusoidal oscillation at a particular frequency, defined as the
oscillating frequency, without an external signal applied. For this to occur two conditions must be met.

The first is that the closed-loop gain computed as the product of the gain of the op-amp multiplied by the gain of
the feedback network of the circuit must be numerically equal to unity.

The gain of the feedback network at the oscillating frequency is equal to 1/32. It follows that the gain of the op-
amp must be approximately equal to or greater than 32 to achieve a unity gain for the closed loop. The needed op-
amp gain is computed as follows:

𝑅𝑃𝑜𝑡 + 𝑅𝑓
29
𝑅𝑖𝑛

The second condition for oscillation to occur is that the phase shift around the closed loop consisting of the op-
amp and the three RC sections is 00. The feedback network provides an overall phase shift of 1800 and the op-
amp will provide a phase shift of -1800 at the oscillating frequency. Its value is computed as follows:

𝑓 𝐻𝑧
How to submit:
a. Present your results on a neat printed practical guide during demonstration clearly indicating you initials,
surname and student number for signature on each page. Also, present page 4 for signature when you’ve
completed the experiment.

b. You are required to take a photograph (or scan) of your signed results.

c. You must paste the photos on a word document and save your photo using the following file name:
2025_EEL125C_Exp num_StudentNumber_StudentSurname. Save the file as .pdf for submittal

d. Upload to eThuto via the Assignment under the Practical Work folder.
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Determining the Vout:

Figure 12

a. Wire the circuit shown in Figure 12 (student ensure it is correctly wired).

b. Connect terminal 7 of the op-amp to the positive terminal of the power supply. Set the voltage of the terminal
to 15 V. Connect terminal 4 of the op-amp to the negative terminal of the power supply. Set the voltage of
the terminal to -15 V.

c. Connect an oscilloscope to the Vout terminal of the phase-shift oscillator.

d. Using the resistance value of R and the capacitance value of C, calculate the theoretical frequency of Vout
using the formula given on the previous page.

f(theoretical) = ………………Hz

e. Adjust the time base of the oscilloscope to obtain several cycles of Vout. Adjust the vertical scale to about 5
V/division. Select AC computing

f. Estimate the approximate resistance setting of RPot for oscillations to occur. Remember that the gain of the
op-amp must be approximately 32.

Estimated Setting of RPot = …………….……..kΩ

g. Carefully adjust the resistance of RPot to obtain oscillations.

Note: if you increase the resistance of RPot, eventually the output sine wave will show clipping. Adjust the
resistance of RPot until the oscillator just sustains oscillations. Record the peak-peak voltage Vout.

Vout (peak-peak) = ………………………V

h. Change the time base so that about two cycles of Vout are displayed. Measure the period of one of these
cycles.

Period = ………………..…ms

i. From the above value for the period of Vout, calculate the value of the experiment frequency obtained.

f(experimental) = ………………Hz

j. Obtain the percent difference between the theoretical and the experimental frequencies using the theoretical
frequency as the standard of comparison.
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𝑓(𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙)−𝑓(𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙)
% 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 𝑥 100
𝑓(𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙)

Calculated % difference = …………………………

k. Disconnect RPot and Rf from the circuit. Use a DMM and measure their combined resistance.

RPot + Rf = ……………….……Ω

l. Using the value of the resistance and assuming that Rin is 1kΩ, calculate the open-loop gain for this oscillator.

Open-loop gain = ………………………

m. Obtain the percent difference between the theoretical gain of 32 and the experimental gain of the op-amp.

Calculated % difference = ……………………….

n. If the experimental frequency and the open-loop gain of the op-amp differ by more than 10% from their
theoretical values, suggest a change of the design to bring those two sets of data within that percent deviation.

Experiment 3 – Equipment required (students may write the equipment serial numbers next to each equipment
used for later reference)

DC power Supply
Oscilloscope

Experiment 3 – Components Needed

Resistors:
Three (3) 1 kΩ
One (1) 27 kΩ
One (1) 1 MΩ
One (1) 0.5 kΩ
potentiometer

Capacitors:
Three (3) 0.1 F
 25

EXPERIMENT 4: frequency response of common-emitter amplifiers

Key Objective: To calculate and measure the frequency response of common-emitter amplifier circuits.

Assessment Criteria: Marks

Building circuits on bread board (Preparation) 6

Simulated results (Preparation, eThuto) 3

Results (eThuto) 19

Reading: Chapter: Boylestad, R. L. & Nashelsky, L. 2013. Electronic Devices and Circuit Theory (11th
Edition). United States of America: Prentice-Hall, Inc.

Resume of Theory: The analysis of the frequency response of an amplifier can be considered in three frequency
ranges: the low-, mid-, and high frequency regions. In the low-frequency region the capacitors used for DC
isolation (AC coupling) and bypass operation affect the lower cut-off (lower 3-dB) frequency. In the midfrequency
range only resistive elements affect the gain, the gain remaining constant. In the high-frequency region of
operation, stray wiring capacitances and device inter-terminal capacitances will determine the circuit’s upper cut-
off frequency.

Lower cut-off (lower 3-dB) frequency: Each capacitor used will result in a cut-off frequency. The lower cut-off
frequency at the network is then the largest of these lower cut-off frequencies.

How to submit:

e. Present your results on a neat printed practical guide during demonstration clearly indicating you initials,
surname and student number for signature on each page. Also, present page 4 for signature when you’ve
completed the experiment.

f. You are required to take a photograph (or scan) of your signed results.

g. You must paste the photos on a word document and save your photo using the following file name:
2025_EEL125C_Exp num_StudentNumber_StudentSurname. Save the file as .pdf for submittal

h. Upload to eThuto via the Assignment under the Practical Work folder.

Part 1: Low-Frequency Response Measurements

Figure 13: Common-Emitter Amplifier Network

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a. Preparation:
You are required to simulate all the measurements of part1 using PSpice, upload them on ethuto and
bring them to the lab to compare with experimental results to be obtained in class.

b. Construct the network of Figure 13. Record the actual resistor values in the space provided in Figure 13.
Adjust VCC = 20 V. Apply an input AC signal, Vsignal = 1Volt peak to peak, at a peak frequency of f = 5 kHz.
Connect channel 1 of the oscilloscope to Vsignal and channel 2 to Vo. Display both signals on the screen of
the scope. If Vo shows any distortion, reduce Vsignal until the output is undistorted.

c. Measure and record signals for undistorted operation.

Vsignal (measured) = ……………………………………. volts (1)

Vo (measured peak to peak) = ……………………….………………..volts (1)

Calculate the circuit’s voltage gain.

Av = ………………………………. (2)

d. Maintaining the input voltage at the level set in Part 1 (a), vary the frequency and measure and record Vo to
complete Table 4.

Table 4: V0 vs. frequency

f (Hz) 50 100 200 500 1k 2k 10k 15k 20k 25k

V0
(Vp-p)

(10)

Calculate the amplifier voltage gain for each frequency and complete.

Table 5: AV vs. frequency

f (Hz) 50 100 200 500 1k 2k 10k 15k 20k 25k

AV

(5)
[25]
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Experiment 4 – Equipment required (students may write the equipment serial numbers next to each equipment
used for later reference)

Oscilloscope
DMM
Function Generator DC
power supply

Experiment 4 – Components Needed

Resistors:
Two (2) 2.2 kΩ
One (1) 3.9 kΩ
One (1) 10 kΩ
One (1) 39 kΩ

Transistors:
One (1) 2N3904 or
equivalent general
purpose NPN

Capacitors:
One (1) 1 uF
One (1) 10 uF
One (1) 20 uF
 28

PRACTICAL TEST 1: BJT Characteristics

Key Objective: To determine transistor type, terminals and material using the multimeter (DMM).
To plot the collector characteristics of a transistor

To determine the value of the beta ratio of a transistor

Resume of Theory: See Tutorial 1 and Experiment 1.

Reading: See Experiment 1.

PRACTICAL TEST 1 – Components Needed

Same as Experiment 2.
 29

SAFETY AND SAFETY PRECAUTIONS

Introduction

Close attention should be given to all aspects of safety throughout training, and the highest possible standards
insisted upon. There is a special need to emphasize the fundamental safety rules of behaviour, dress and practice
when the trainee enters the workshop. Instructors have a particular responsibility to set a good example and to
check without delay any departure from safe working practices by trainees. Individual responsibilities in respect
of the safety of all persons in the vicinity of the working area must be clearly understood by everyone. It is essential
to develop safe working habits.

General safety

What to do

o Think before you act.

o Ask if in any doubt.
o Help to keep gangways clear.
o Keep your bench and working area tidy.
o Find out the position and type of fire appliances
available.

o Report all accidents to your supervisor.

What not to do

o Do not run.

o Do not play practical jokes.

o Do not touch any equipment or try out machines unless authorized to do so.
o Do not leave rubbish lying about.

o Do not walk under suspended loads.

o Do not attempt to give first aid unless you are competent to do so.

o Do not throw things.

Further points to consider

o Wear your overalls buttoned up.

o Roll up your overall sleeves above the elbows or button up the cuffs.
o Keep hair short or wear a cap.
o Obey all safety rules and signs.
o Report any accident, however slight.
o Have all injuries properly treated, however minor.

o Do not wear torn overalls.

o Do not wear rings or a watch when working.

o Do not take chances.

 30

Safety and Electricity

Electric shock

Care must be taken when working with electricity, in order to reduce the risk of electric shock. An electric shock
is when an electric current passes through the body; what happens to the body depends on the size of the current.
One milliamp is the largest safe current. Two to five milliamps feel very unpleasant to most people. A current of
10 milliamps causes muscular spasms which make it difficult to move. One hundred milliamps passing through
the heart will kill within a second. Currents larger than this will kill instantly. The size of the current depends on
the voltage and also the resistance of the body. The resistance decreases if the body is wet.

How to avoid electric shock

The following procedure should be adopted when working with electricity to minimize the risk of an electric
shock:

o Always use low voltages (less than 50 V).

o Use currents less than five milliamps.
o Hands should always be dry.

o Work area should be kept dry and clean.

o Both hands should never be touching the equipment at

the same time.

Treating electric shock

1 Switch off the supply. If this is not possible then pull the victim away using an insulator such as a piece
of dry wood, a piece of rope or clothing. Do not use your hands.
2 Send for help. Preferably this should be someone qualified in First Aid.
3 Check the heart and breathing. If there is no sign of breathing or heartbeat, then apply artificial respiration
and if you are properly trained apply chest compression if this is considered necessary.
4 Burns should be treated immediately with cold water and then covered with a clean, dry cotton cloth
until help arrives.
5 The person may be in a state of shock and therefore it is important that the person remain either sitting
or lying down and be kept warm. An unconscious person should be placed on their side and not be given
food or drink as there is a risk of choking.
6 Fill in an accident report form. If you are not in a position to do this, then a report should be given to
someone who is in a position to fill in the form.

Electrical Safety

1 Mains plugs must be correctly fitted and the cable securely held by the cord precautions grip.
2 Plugs must have the correct fuse fitted and circuits going to the consumer unit must be protected by fuses
of the right value.
3 Fuses, single-pole switches and all types of circuit breakers must be fitted to the 'live' wire of mains
equipment.
4 Holes through which flexes enter an appliance must have a rubber grommet (rubber washer) to protect
the outer insulation of the flex from unnecessary wear. In addition, the flex should be held by the strain
relief cable clamp fitted inside the appliance.
5 There is a legal requirement for all electricity supplies to be earthed. This is done at the electricity
substations and IEE (Institute of Electrical Engineers) members also ensure that this is done at the
consumer unit in the home.
6 Special care should be taken when working with capacitors as these can store a large charge for a long
time after the supply has been disconnected. Capacitors should be discharged by shorting the terminals
with an insulated conductor.
 31

General safety precautions

Hand tools

All tools must be used in a safe manner, in particular sharp tools such as knives or screwdrivers. These should be
held in such a way as to minimize the chances of cuts to the user if they slip from the work. The snipping of wires
with side-cutters can lead to bits of wire entering the eye and therefore goggles should be worn for such work.

Power tools

These tools must be electrically safe and should be inspected regularly for cable wear and loose connections. They
should never be used without a guard or some form of protection fitted and adjustments to these tools should only
be made once they have been disconnected from the supply.

Soldering irons

Soldering irons should always be kept covered to prevent accidents leading to burning of the skin or of the flex of
the soldering iron. The work being soldered or de-soldered should be securely gripped and the work should take
place on a heat-proof mat. Excess solder should be wiped off using a wet cloth or sponge and should not be flicked
off. Care should also be taken to avoid breathing in the fumes of the flux.

Protective clothing

Whether or not this is worn depends on the regulations and on the work taking place in the workshop. Long hair
should be tied back and if hair preparation is used the hair should also be covered whenever working close to a
naked flame.

References

New Diploma Industrial Technology - V.R. Hamilton (Nasou Limited); Chapter 1 Basic Electronics for
Tomorrow’s World - Len Jones