Experiment 10: Inverting Amplifier With Modifications that Require the Use of the Velleman...
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![Page 1: Experiment 10: Inverting Amplifier With Modifications that Require the Use of the Velleman Oscilloscope.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697c01b1a28abf838ccf9b1/html5/thumbnails/1.jpg)
Experiment 10: Inverting Amplifier
With Modifications that Require the Use of the Velleman Oscilloscope
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Figure 1: Circuit Diagram for Inverting Amplifier
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Additional Steps
• Modeling in PSpice– Simulate the transient response of the inverting
amplifier circuit using• Part E, a voltage controlled voltage source
– The difference in voltage between the two input terminals of an op amp cause an output voltage to be generated.» Ideal Op Amp model
• Part LM324» Close to a real Op Amp model
– The sinusoidal voltage source that must be used for a transient analysis is Part Vsin.
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Circuit A with Part E:Schematics
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Op Amp Equivalent Circuitvd = v2 – v1
A is the open-loop voltage gain
v2
v1
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Typical Op Amp ParametersParameter Variable Typical Ranges Ideal ValuesOpen-Loop
Voltage GainA 105 to 108 ∞
Input Resistance
Ri 105 to 1013 W ∞ W
Output Resistance
Ro 10 to 100 W 0 W
Supply Voltage Vcc/V+
-Vcc/V- 5 to 30 V
-30V to 0VN/AN/A
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Voltage Transfer Characteristic
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Set Open Loop Gain
• Double click on symbol and set GAIN to at least 100,000– Typical open loop gain of an op amp is 105-108 V/V
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Setting the Attributes on Vsin:Schematics
Double click on the symbol for V1. A pop-up window will open.
Change: VOFF (the dc offset voltage) to 0V. VAMPL to 5V. FREQ to 500Hz.
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Circuit A with Part E:Capture
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Open Loop Gain
• Double click on symbol for Part E.• Set GAIN in Property Editor pop-up window to
at least 100,000.
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Setting Attributes on Vsin:Capture
• Double click on the labels (VOFF, VAMPL, and FREQ) individually in schematics and change their value in the pop-up window that opens.
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Setting Attributes on Vsin:Capture
• Or, click on the symbol for Vsin and change the values for the attributes in the Property Editor pop-up window. – FREQ is at the left side, VOFF and VAMPL are at
the far right side.
Scroll right to find VOFF and VAMPL
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Circuit B with LM324:Schematics
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Simulation Set-up:Schematics
Final Time should be 3-5 times the period (T) of V1.
T = 1/f where f is the frequency of the sinusoidal signal.
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Simulation Profile:Capture
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Plot of the input voltage and output voltage as a function of time
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Modifications to Measurement Section: New Circuit
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Cables
• The connections to the Velleman scope are BNC (Bayonet Neill-Concelman) connectors.– You will need to use 3 BNC cables with either the
alligator clips or the IC clips to make your connections between the scope and your circuit.
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Input Voltage Source
• Use the sine wave generator on the Velleman scope.– Set the amplitude of the sine wave to 5V
• Note that the amplitude on the Velleman scope is actually peak-to-peak so you should actually make this 3V.
– Set the frequency of the sine wave to 500Hz.
– Connect BNC cable to function generator (bottom BNC connection). • Clip red probe to end of R2. • Clip black probe (ground) to end of R1.
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Voltage Measurements using Oscilloscope
• Channel 1:– Red probe placed between function generator and
R2.– Black probe connected to same point as the black
wire from the function generator.• Channel 2:– Red probe placed between output of the LM 324
and the feedback resistor, R5.– Black probe connected to same point as the black
wire from the function generator.
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Measurements
1. As suggested in lab manual, set trim pot value such that the output voltage of the op amp is equal to -3V when the input voltage is +1.5V.– Take a screen shot of the input and output voltage as a function of
time, displaying at least 3 cycles.– Remove R5 from the circuit. Measure and record the resistance
between pins 1 and 2.– Measure the output voltage at the following input voltages:
• 0V, +/-1V, +/-2V, +/-3V, +/- 4V, +/-5V, and +/-6V – use cursors in scope program
– Plot the output voltage as a function of the input voltage.• Determine
– the gain of the inverting amplifier in the linear region of the voltage transfer characteristic using a least squares determination of the slope in the linear region
– the output voltage at the positive and negative saturation regions.
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Measurements
2. Set trim pot value such that the output voltage of the op amp is equal to -4.5V when the input voltage is +1.5V.– Take a screen shot of the input and output voltage as a function of
time, displaying at least 3 cycles.– Remove R5 from the circuit. Measure and record the resistance
between pins 1 and 2.– Measure the output voltage at the following input voltages:
• 0V, +/-1V, +/-2V, +/-3V, +/- 4V, +/-5V, and +/-6V – use cursors in scope program
– Plot the output voltage as a function of the input voltage.• Determine
– the gain of the inverting amplifier in the linear region of the voltage transfer characteristic using a least squares determination of the slope in the linear region
– the output voltage at the positive and negative saturation regions.
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Measurements
3. Set trim pot value such that the output voltage of the op amp is equal to -6V when the input voltage is +1.5V.– Take a screen shot of the input and output voltage as a function of
time, displaying at least 3 cycles.– Remove R5 from the circuit. Measure and record the resistance
between pins 1 and 2.– Measure the output voltage at the following input voltages:
• 0V, +/-1V, +/-2V, +/-3V, +/- 4V, +/-5V, and +/-6V – use cursors in scope program
– Plot the output voltage as a function of the input voltage.• Determine
– the gain of the inverting amplifier in the linear region of the voltage transfer characteristic using a least squares determination of the slope in the linear region
– the output voltage at the positive and negative saturation regions.
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Measurements
• Measure exact values of V+ and V- powering the LM 324 op amp.
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Tabulate ResultsVout when Vin is equal to 1.5V
Gain from Analysis
Measured Value of R5
Gain from Least Square Fit of Data
% Deviation of the Gain
-3V
-4.5V
-6V
Vout when Vin is equal to 1.5V
Averaged Measured Positive Saturation Voltage
Measured Value of V+
Averaged Measured Negative Saturation Voltage
Measured Value of V-
% Deviation for positive saturation voltage
% Deviation for negative saturation voltage
-3V
-4.5V
-6V
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Discussion Section
• Compare the gains found in Analysis Section and the measured results.– Explain any discrepancies
• Explain the major differences between the two PSpice simulations.
• Compare the averaged positive and negative saturation voltages with the measured values of the power supplies. – Does the saturation voltage depend on the amplifier gain
(within experimental error)?– Does the saturation voltage agree with that specified in the
LM 324 data sheet (find on-line)?
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