Lab #5
Op-Amps
Due: Start of NEXT Class (Monday)
Name / SN:____________________________________
TA:
__________
Name / SN:____________________________________
TA:
__________
A) Pick up the following components from the TA:
1.
2.
3.
4.
5.
6.
LM324 Quad Op-Amp (1)
1K resistor (2)
2K resistor (1)
5.1K resistor (2)
10K resistor (1)
100nF capacitor (1)
B) Power the LM324 IC with Vcc = ±12V. Connect V+ to V-.
1.
With V+ = V-, the output voltage should be 0V. What output voltage do you measure?
Why isn’t it 0?
Ans:
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Vout
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Explain
C) Connect V+ to +12V and V- to -12V.
1.
Look up the voltage gain of the op-amp from the datasheet.
Ans:
2.
____________________________________
Gain
Compute the theoretical output voltage that you should measure. What output voltage do
you actually measure? Why are the two values so different? What is this mode of operation called?
Ans:
____________________________________
ECE 251 - Circuit Analysis I
Theoretical
Department of Electrical & Computer Engineering, UBC
Ans:
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Actual
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____________________________________
Explain
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Mode
D) Use the 1K and 2K resistors to create an inverting amplifier which has a gain
of -2. Use the fixed voltage supply to apply an input voltage of 5V. Connect a
1K resistor between the output of the op-amp and ground.
TA: ____________________________________
1.
What is the output voltage?
Ans:
2.
____________________________________
Vout
Measure the current provided by the input supply and the current through the output
resistor.
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____________________________________
Iin
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Iout
3.
Why are these different? Where is the additional current coming from?
Ans:
____________________________________
ECE 251 - Circuit Analysis I
Explain
Department of Electrical & Computer Engineering, UBC
E) Build a summing amplifier with the following behaviour. Use a 5VDC input for
V1 and use the signal generator to supply a sinusoidal input with 1Vpeak and
1KHz for V2.
V out = – V 1 – 2.55 V 2
TA: ____________________________________
1.
Use the scope to measure the signal generator voltage and the output voltage. Sketch
them and label the axes.
BONUS TASKS:
F) Build the differentiator circuit shown below with C=100nF and R=10K. Use the
signal generator to apply a sinusoidal input with 1/2Vpeak and 1KHz to the input
1.
Use the scope to measure the signal generator voltage and the output voltage. Sketch
them and label the axes.
ECE 251 - Circuit Analysis I
Department of Electrical & Computer Engineering, UBC
2.
Does the output lead or lag the input? Is this what you would expect? Why?
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Lead/Lag
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Explain
3.
Make small adjustments to the offset voltage on the signal generator and observe how it
affects the output. What does it do? Is this what you would expect? Why?
Ans:
4.
____________________________________
Switch the input signal to a triangle wave? What shape is the output? Does this make
sense? Why?
Ans:
____________________________________
ECE 251 - Circuit Analysis I
Explain
Department of Electrical & Computer Engineering, UBC