EEE1046 Electronics III
Experiment ECT1
FACULTY OF ENGINEERING
LAB SHEET
ELECTRONICS III
EEE1046
TRIMESTER 2 (2015/2016)
ECT1: Operational Amplifiers
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EEE1046 Electronics III
Experiment ECT1
EEE1046 Electronics III
Experiment ECT1: Operational Amplifiers and Their Typical Applications
1.0 Objective
 To understand the basics of integrated circuit (IC) operational amplifier 741.
 To illustrate typical applications of op-amp circuits.
2.0 Apparatus
Equipments required:
a) Oscilloscope.
b) Regulated Power Supply – Two single-output power supplies or a dual-output power
supply that could produce positive and negative voltages.
c) Function generator.
d) Digital multimeter.
e) Breadboard, and some single core wires.
Components required (quantities shown within parenthesis):
a) Resistors (0.25W, carbon film) – 10k (4), 33k (1)
b) Potentiometer (0.5W or 1W) – 100k (1).
c) Operational Amplifier (dual-in-line package): 741 (1).
d) Capacitor – electrolytic 10F/16V (2)
3.0 Introduction
Operational amplifiers are integrated circuits capable of amplification and operation of
analog signals (ac or dc). Usually the output of an operational amplifier is the amplification
of the difference of the signals at its two input terminals. Internally the op-amp is made up of
three basic circuits: a high input impedance differential amplifier, a high gain voltage
amplifier and a low impedance output amplifier. These three circuits deal with the three most
important characteristics of an op-amp:
1.
2.
3.
High input impedance: results in minimal loading and therefore negligible currents
produced at the inputs.
High open loop gain: provides a wide range of closed loop applications.
Low output impedance: gives the ability to drive a wide variety of loads with little
effect on the output voltage.
A general purpose IC Op-amp has two input terminals (the inverting or negative input and the
non-inverting or positive input), an output terminal, two voltage supply terminals (positive
and negative) and terminals for offset adjustments. The 741 is a general purpose integrated
circuit (IC) operational amplifier. It is typically housed in an eight-pin plastic package
known as plastic dual-in-line (plastic DIP). The assignment of pin functions for 741 is shown
in Figure 1.
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EEE1046 Electronics III
Experiment ECT1
1(offset adj)
8(not connected)
2(inverting
input)
–
3(noninvert
input)
+
4(-ve supply)
V+
V–
7(+ve supply)
6(output)
5(offset adj)
Figure 1 - Operational Amplifier 741 Pin Diagram.
4.0 Experiments
Instructor’s checks & On-The-Spot Evaluation:
The instructor will check as to whether you have done a proper job before allowing you to
proceed to the next experiment. You will be asked to repeat your work if your results are not
of a satisfactory level. All results – both displayed (oscilloscope), and sketched (graph), are to
be shown to the instructor.
On-The-Spot Evaluation:
On the spot evaluation is individual and will take into consideration of individual
commitments towards the experiments such as self-preparation, punctuality, self-initiative,
active participation, cooperation, good learning attitude, team work and efforts.


Students are responsible to ask the instructor to check their experimental results
before proceeding to the next experiment.
On-The-Spot Evaluation will be carried out throughout the experiments to assess
the students’ participation and commitments in the experiments.
Note: Circuit is not working but experimental results are correct – Cheating (0 marks)
Circuit construction:
Construct the following circuits using operational amplifier 741 and other circuit elements as
shown in the diagrams and follow the procedures outlined for each.
Pins not connected:
In all these experiments, pins 1, 5 and 8 of integrated circuit 741 are left not connected. Pins
1 and 5 are for offset voltage adjustment, of which can be ignored at this stage.
Caution on the oscilloscope:
Make sure the INTENSITY of the displayed waveforms is not too high, as it can burn the
screen of the oscilloscope.
Caution on the function generator:
Never short-circuit the output, which may burn the output stage of the function generator.
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Experiment ECT1
Oscilloscope setups:
1. Check that all the 3 variable (VAR) knobs are at their calibrated (CAL’D) positions.
2. Set DC input coupling for both channels for all the experiments.
3. Position the channel ground levels as indicated in the lab report form.
4. Set time/div to display one to two cycles of waveforms.
5. Set volts/div for most accurate measurement (at least covering 3.2 vertical divisions).
6. Other settings – as that you have learned in your past experiments in the previous
trimesters.
Sketching of the waveforms:
1. Use the waveform sketching technique you learned during Electronics 1 lab experiments
(Appendix D). You are assumed to already have the skill.
2. All waveforms must be sketched on the graphs given in the short report form.
3. All waveforms sketched must be as per displayed on the oscilloscope screen.
4. Vout(t) must be sketched with respect to Vin(t).
5. Time/div and volts/div must be recorded.
Positive and negative (with respect to ground) DC voltage supplies:
Method for obtaining positive and negative voltage supplies from two single power supplies
is illustrated in Figure 2a.
Power Supply 1
-
GND
Power Supply 2
+
-
GND
+
-10V
GND
+10V
Figure 2a – Obtaining +10V and –10V from single power supplies
Smoothing capacitors:
These capacitors provide low inductance current paths for high frequency (in MHz) or
transient (rising and falling of square waves) signals. They stabilize the voltage at the DC
supply voltage lines, and reduce the inductive effect on output waveform distortion. Connect
two smoothing capacitors on the breadboard as indicated in Figure 2b and Appendix B. Note
that the capacitors are polar type whereby the negative terminal (as indicated on the capacitor
casing) must be connected to the lower potential end (otherwise, an explosion may occur).
+10V
+
From
power
supplies
10F
GND
+
10F
-10V
Figure 2b – Smoothing capacitors on breadboard.
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Experiment ECT1
4.1 Inverting Amplifier
Rf =33k
+10V
Vin
R1=10k 2
3
–
7
V+
+
V–
4
6
Vout
-10V
Figure 3 – Inverting Amplifier
Procedures
(a) Calculate Vout(pp) [the peak-to-peak voltage of Vout] using the equation below and record in
the lab report. Assume that Vin(pp) = 1.0V [Vin(pp) is the peak-to-peak voltage of Vin],
Rf
Vout  
Vin , negative (-) sign indicates 180o phase shift
R1
(b) Construct the circuit as shown in Figure 3 (refer to Appendix B for breadboard
connections). Double-check the power supply voltages before connect the power supply
outputs to the circuit.
(c) Using a function generator, apply a 1.0V peak-to-peak sine wave of 1 kHz to the input Vin
of the inverting amplifier shown in Figure 3.
(d) Set proper time/div and volts/div as mentioned in page 2. Why do we need to set the
proper time/div and volts/div? Justify your answer.
(e) Measure Vout(pp) (this measured value should be around the predicted value) and
record the phase shift of Vout with respect to Vin (). Calculate the ratio
Vout(pp)/Vin(pp). Sketch the waveforms of Vin and Vout. Interpret the observation of the
displayed waveform to the instructor.
(f) Ask the instructor to check all of your results. Show your last oscilloscope-displayed
waveforms to the instructor.
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Experiment ECT1
4.2 Noninverting Amplifier
Rf =33k
+10V
R1=10k 2
Vin
3
–
7
V+
+
V–
4
6
Vout
-10V
Figure 4 - Noninverting Amplifier
Procedures
(a) Calculate Vout(pp) using the following equation (with Vin(pp) = 1.0V):
 Rf 
Vin
Vout  1 
R1 

(b) Construct the circuit as shown in Figure 4. Apply a 1.0V peak-to-peak sine wave of 1 kHz
to the input Vin. Measure Vout(pp) and record . Calculate the ratio Vout(pp)/Vin(pp). Sketch
the waveforms of Vin and Vout. Interpret the observation of the displayed waveform to the
instructor.
4.3 Buffer
+10V
2
Vin
3
–
7
V+
+
V–
4
6
Vout
-10V
Figure 5 - Noninverting Buffer / Voltage Follower.
Procedures
(a) Construct the circuit as shown in Figure 5. Apply a 1.0V peak-to-peak sine wave of 1 kHz
to the input Vin. Measure Vout(pp) and record . Calculate the ratio Vout(pp)/Vin(pp). Sketch
the waveforms of Vin and Vout. Interpret the observation of the displayed waveform to the
instructor.
(b) Ask the instructor to check all of your results. Show your last oscilloscope-displayed
waveforms to the instructor.
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4.4 Quantizer or Comparator
V
+10V (from DC pow er supply)
X
R2 33k
Y
R1
10k
100k
pot
+10V
Vref
2
Vin
3
–
+
7
V+
V–
4
Vref = 0.3V
6
Vout
tw
0V
Vin
t
tw1
-10V
Figure 6a - Op-amp Comparator Circuit (non-inverting).
Figure 6b – Comparing Vin and Vref
(Refer to Appendix A for potentiometer (pot) connections.)
Procedures
(a) Solve Vin = Vref to determine the width tw1 and then tw. You are told that: Vin = 0.5sint,
where  = 2f and f = 1kHz, and Vref = 0.3V. (Note:  radians = 180o). Calculate tw/T,
where T is the time period.
(b) Construct the circuit as shown in Figure 6a. Use multimeter to check the supply voltages
are +10V and -10V. Adjust the potentiometer to get Vref = 0.3V (measured by a
multimeter at pin 2).
(c) Apply a 1.0V peak-to-peak sine wave of 1 kHz to the input Vin. CH1 and CH2 must use
DC input coupling. Set CH2 volts/div to display the whole waveform.
Notes: Function Generator output offset voltage (if any)
Check the function generator output offset voltage (the average voltage) is zero (0V).
If not, manually adjust it to zero before measurements.
(d) Measure Vout(+sat), Vout(-sat), T and tW. [Vout(+sat) is the Vout positive saturation voltage. Let
tW is the width when Vout = Vout(+sat)].
(e) Calculate tW/T based on the output obtained. Sketch the waveforms of Vin and Vout.
(f) Observe the Vout changes by varying Vref between 0V (at the Y side) and 0.5V (no data
recording is required for this observation). Interpret the observation of the displayed
waveform to the instructor.
Report Submission
You are to submit your report immediately upon completion of the laboratory session.
End of Lab Sheet
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