ECE 323L Basic Electronic Circuits Laboratory
Lab 11
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Do the following exercises. Report your results by editing this Word document and submitting it in WebCT.
This laboratory explores some circuits using the LM348 operational amplifier, the same IC you used in laboratory 3. You will use the triple-output DC supply on the lab bench to provide the ±12-volt power to the op-amp. Figure 6 at the end of this document shows recommended power connections. Connect the 12-volt supply to Va and the -12-volt supply to Vb. Connect the COM output to ground. The pin diagram for the LM348 is reproduced in Figure 1.
Figure 1. Pin Diagram of LM348 IC
- Construct
the inverting amplifier circuit shown in Figure 2, with resistances
Rf = 470 kW, Rs = 47 kW, and RC = 10 kW.
a) Measure the gain and phase shift at the following frequencies. Calculate the ideal gain from the nominal resistance values.
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Freq |
Gain |
Phase |
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Ideal |
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100 Hz |
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1 kHz |
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10 kHz |
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100 kHz |
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Figure 2. Inverting amplifier.
b) Measure the saturation (clipped) peak-to-peak level at 1 kHz. Set the input so that the ideal output value would be 25 volts peak-to-peak. Attach an image of the oscilloscope output to the report.
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c) Measure the slew rate by using a 10-kHz square-wave input. Measure the rise and fall times and the peak-to-peak output voltage. Attach an image of the oscilloscope output to the report.
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Rise/Fall time |
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Calculated slew rate |
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d) Find a frequency at which the output looks distinctly triangular. Attach an image of the oscilloscope output to the report.
e) Find the frequency at which the phase has shifted by 20-degrees and the frequency at which the gain has dropped by one-half. Attach images of the oscilloscope output to the report.
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Freq for 20-degree phase shift |
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Freq for which gain drops by one-half. |
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- Construct
the noninverting amplifier circuit shown in Figure 3, with resistances
Rf = 140 kW, Rs = 47 kW, and RC = 10 kW.
Figure 3. Noninverting amplifier
Measure the gain and phase shift at the following frequencies. Calculate the ideal gain.
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Freq |
Gain |
Phase |
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Ideal |
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100 Hz |
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1 kHz |
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10 kHz |
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100 kHz |
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1 Mhz |
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- Construct the voltage-follower circuit shown in Figure 4.
Figure 4. Voltage follower
Measure the gain and phase shift at the following frequencies.
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Freq |
Gain |
Phase |
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100 Hz |
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1 kHz |
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10 kHz |
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100 kHz |
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1 Mhz |
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- Construct
the cascaded amplifier circuit shown in Figure 5, with resistances
R1 = R5 = 47 kW, R2 = 470 kW, R4 = 22 kW, R1 = 47 kW, R2 = 470 kW, and
R3 = R6 = 10 kW.
Figure 5. Cascaded amplifier
Measure the gain and phase shift at 100 Hz and 1 kHz. Calculate the expected gain
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Freq |
Gain |
Phase |
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Ideal |
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100 Hz |
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1 kHz |
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10 kHz |
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100 kHz |
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1 Mhz |
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Figure 6. Connecting prototype board to the triple-output power supply.
maintained by John Loomis, updated 24 March 2008