ENGR 43
Lab Activity
Student Guide
LAB 13 – Op-Amp Amplifier Circuits
Student Name: ___________________________________________________
Overview
Getting Started
Operational Amplifiers (Op-Amps) are the
most common building block for analog
circuits. Although large-scale integration
(LSI) integrated circuits are now standard
for analog systems, op-amps are still used
for routine functions.
Lab Activity and Deliverables:
It should take students approximately 3
hours to complete the lab activity, and 1
hour of homework time to complete the lab
report.
Equipment & Supplies
Before Starting This Activity


Item
NI-ELVIS
LM358 dual op-amp
0.1 µF capacitors
10 kΩ resistors (brown, black,
orange)
47 kΩ resistor (yellow, violet,
orange)
100 kΩ resistor (brown, black,
yellow)
220 kΩ resistor (red, red, yellow)
The student should be familiar with the
basic inverting and non-inverting
amplifier configurations for op-amps.
Download the data sheet and review the
pin-out configuration for the LM358 opamp from Texas Instruments,
www.ti.com
Learning Outcomes For Activity
Relevant knowledge (K), skill (S), or
attitude (A) student learning outcomes
Special Safety Requirements
K1. Calculate gain for inverting and noninverting op-amp amplifier circuits
None
S1. Breadboard op-amp circuits
Lab Preparation
S2. Test and troubleshoot op-amp circuits
This lab requires the NI-ELVIS with the
standard prototype board installed.
A1. Appreciate the capabilities of op-amps
for multiple circuit applications.
Lab 13 – Op-Amp Amplifier Circuits
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Lab Activity
Student Guide
Task #1 – Non-Inverting Amplifier
4. Calculate the amplifier gain Av, using
the formula Av=Vout/Vin
Note: The data sheet for the LM358 may list
the supply voltage pins as +V and Ground.
This is for single-supply operation. Our
circuits use dual-supply operation with
+15V and -15V supplies. The +15V goes to
pin 8, the -15V goes to pin 4. DO NOT
connect pin 4 to ground!
Av=_________ (note: gain is a ratio, so
it has no units)
5. Calculate the gain using the formula
Av= 1+ Rf/Ri
Av=________
How do the two gain calculations
compare?
_______________________________
6. Examine the channels 0 and 1 traces on
the scope. What can you conclude about
the phase relationship of the two signals?
Figure 1
________________________________
7. Repeat steps 3-5 with Rf=47 kΩ
1. Connect +15V to pin 8, and -15V to pin
4. To minimize potential stability
problems with the op-amp, add a 0.1 µF
capacitor from +15V to Ground, and
another 0.1 µF cap from -15V to
Ground. Place the caps as close as
practical to the LM358.
2. Refer to the spec sheet to determine the
pin connections for the circuit in figure
1. The LM 358 has two op-amps in the
package. Choose one of the two, and
mark on Figure 1 the pin numbers for the
inputs and output. Construct the circuit
with Rf = 10 kΩ and Ri=10 kΩ. Set the
function generator for 100 mVpp
sinewave output at 1 kHz and connect it
to the non-inverting input of the op-amp
3. Measure the input voltage with channel
0 of the scope. Measure the output
voltage with channel 1 of the scope.
Vin = ______Vpp, Vout = ______Vpp
Av(meas)=_______, Av(calc)=_______
8. Repeat steps 3-5 with Rf=100 kΩ
Vin = ______Vpp, Vout = ______Vpp
Av(meas)=_______, Av(calc)=_______
9. Leave this circuit connected for later
use.
Vin = ______Vpp, Vout = ______Vpp
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Lab Activity
Student Guide
5. Examine the channels 0 and 1 traces on
the scope. What can you conclude about
the phase relationship of the two signals?
Task #2 – Inverting Amplifier
________________________________
Note that when the output is 180° out of
phase with the input, this can be shown
by listing Av as a negative number.
6. Repeat steps 3-5 with Rf=47 kΩ
Figure 2
Vin = ______Vpp, Vout = ______Vpp
1. Refer to the spec sheet to determine the
pin connections for the circuit in figure
2. Use the other op-amp in the LM 358
package. Mark on Figure 2 the pin
numbers for the inputs and output.
Construct the circuit with Rf = 10 kΩ
and Ri=10 kΩ. Set the function generator
for 100 mVpp sinewave output at 1 kHz
and connect it to the open lead of the
inverting input resistor, Ri.
2. Measure the input voltage with channel
0 of the scope. Measure the output
voltage with channel 1 of the scope.
Av(meas)=_______, Av(calc)=_______
7. Repeat steps 3-5 with Rf=100 kΩ
Vin = ______Vpp, Vout = ______Vpp
Av(meas)=_______, Av(calc)=_______
8. What can you conclude about the
measured vs. calculated gains for opamps?
______________________________
______________________________
9. Can you think of one or more conditions
that would result in the actual gain not
matching the calculated value?
Vin = ______Vpp, Vout = ______Vpp
3. Calculate the amplifier gain Av, using
the formula Av=Vout/Vin
_________________________________
Av=_________ (note: gain is a ratio, so
it has no units)
4. Calculate the gain using the formula
Av= Rf/Ri
_________________________________
10. Leave this circuit connected for use in
the next task.
Av=________
How do the two gain calculations
compare?
_______________________________
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Lab Activity
Student Guide
6. Measure the input and output voltages
and calculate the gain with
Av=Vout/Vin. Does the calculated value
match the measured value now?
Task #3 – Cascading Amplifiers
1. Verify that both amplifiers have the 100
kΩ feedback resistors (Rf) installed.
2. Connect the output of the non-inverting
amplifier (Figure 1), to the input of the
inverting amplifier (Figure 2) as shown
below in Figure 3. Connect the function
generator to the input of the noninverting amp. Set the function generator
for 100 mVpp sinewave output at 1 kHz.
_______________________________
7. Increase the function generator voltage
to 200 mVpp. What is the name for the
effect you are seeing on the output of the
amplifier?
________________________________
Figure 3
3. Connecting the output of one amplifier
to the input of another is known as a
cascade configuration. In this
configuration, the total gain, from the
input of the first stage to the output of
the second stage, is the product of the
gains of the two stages: Avtotal=Av1*Av2.
Calculate the total gain with Rf=100 kΩ
in both stages.
Avtotal=________________________
4. Measure the input voltage on channel 0
and the output voltage on channel 1.
Why doesn’t your measured output
match you calculation?
________________________________
________________________________
5. Replace 100 kΩ Rf in the non-inverting
amplifier (the first stage) with a 10 kΩ
resistor. Now what is the calculated total
gain of the cascaded amplifiers?
Avtotal=________________________
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Lab Activity
Student Guide
5. Enter the output voltages in the table
below with the 100 mVpp input applied
to the inputs as indicated.
Task #4 – Summing Amplifier
100 mVpp input
Figure 4
1. Disconnect the non-inverting amplifier
circuit. Modify the inverting amplifier to
make the summing amp shown in Figure
4.
2. Set the function generator for 100 mVpp
sinewave output at 1 kHz. Connect the
function generator output to Vin1.
Measure the input and output voltages,
and calculate the gain (Vout/Vin).
Vin1
Vin2
Vin3
N
N
N
N
N
Y
N
Y
N
N
Y
Y
Y
N
N
Y
N
Y
Y
Y
N
Y
Y
Y
Vout
(mVpp)
6. This is a crude implementation of what
kind of device?
Vin=______, Vout=______, Av=______
3. Remove the func gen signal from Vin1
and connect it to Vin2. Measure the input
and output voltages, and calculate the
gain (Vout/Vin).
________________________________
Vin=______, Vout=______, Av=______
4. Remove the func gen signal from Vin2
and connect it to Vin3. Measure the input
and output voltages, and calculate the
gain (Vout/Vin).
Vin=______, Vout=______, Av=______
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Lab Activity
Student Guide
Task #5 – Comparator
Task #6 – Schmitt Trigger
Figure 5
Figure 6
5. Modify the comparator to construct the
Schmitt trigger circuit shown in Figure
6. Set the function generator for 5 Vpp
triangle output at 1 kHz, and connect to
Vin.
6. Measure the input and output with the
scope. What is the shape of the output
waveform?
1. Connect the circuit as shown in Figure 5.
Change the power supply voltages to
+5V and -5V Set the function generator
for 5 Vpp triangle output at 1 kHz, and
connect to Vin.
2. Measure the input and output with the
scope. What is the shape of the output
waveform?
______________________________
______________________________
What is the output voltage?
What is the output voltage?
Vout = ____________ Vpp
Vout = ____________ Vpp
3. Change the function generator voltage
output to 1 Vpp. Observe the output
voltage. Change the func gen output to
0.5 Vpp. What can you conclude about
the output voltage as the input voltage
changes?
How does the output differ from the
comparator circuit? (hint: Look at the
7. Change the func gen output to 1 Vpp.
Change the func gen DC offset to -1V,
and step the offset voltage up to +1V in
several steps. What effect does the offset
have on the output voltage of the
comparator, and how does it differ from
the comparator?
_______________________________
_______________________________
4. Change the func gen output to 1 Vpp.
Change the func gen DC offset to -1V,
and step the offset voltage up to +1V in
several steps. What effect does the offset
have on the output voltage of the
comparator?
________________________________
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_______________________________
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Deliverable(s)
_______________________________
Save this activity sheet in your Lab Activity
Binder.
Lab 13 – Op-Amp Amplifier Circuits
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