ECE 201L Circuit Analysis Laboratory
Lab 8

This lab explores some circuits using the LM348 operational amplifier

Do the following exercises. Report your results by creating a Word document and submitting it in Isidore. Submit one report per group.

This laboratory explores some circuits using the LM348 operational amplifier, which you should find in the blue toolboxes and in your parts kit. 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

  1. Construct the inverting amplifier circuit shown in Figure 2. Choose RC = 10 kΩ and Rf and Rs to produce a gain of -8.

    1. Measure the gain and phase shift at the following frequencies.

      Frequency 400 Hz700 Hz1 kHz5 kHz10 kHz50 kHz

    2. Find the frequency and gain at which the phase has shifted by 20° and shifted by 45°


    Figure 2. Inverting amplifier

  2. Construct the noninverting amplifier circuit shown in Figure 3, with resistances Rf = 140 kΩ, Rs = 47 kΩ, and RC = 10 kΩ. Calculate the ideal gain and phase shift from the nominal resistance values. Measure the gain and phase shift at the following frequencies.

    Frequency 400 Hz700 Hz1 kHz5 kHz10 kHz50 kHz


    Figure 3. Noninverting amplifier

  3. Construct the voltage-follower circuit shown in Figure 4. Measure the gain and phase shift at the following frequencies.

    Frequency 400 Hz700 Hz1 kHz5 kHz10 kHz50 kHz


    Figure 4. Voltage follower.

  4. Construct the cascaded amplifier circuit shown in Figure 5, with resistances R1 = R5 = 47 kΩ, R2 = 470 kΩ, R4 = 22 kΩ, R1 = 47 kΩ, R2 = 470 kΩ, and R3 = R6 = 10 kΩ. Calculate the ideal gain and phase shift from the nominal resistance values. Measure the gain and phase shift at the following frequencies.

    Frequency 400 Hz700 Hz1 kHz5 kHz10 kHz50 kHz


    Figure 5. Cascaded amplifier


Connecting prototype board to the triple-output power supply


Figure 6. Connecting prototype board to the triple-output power supply.


Maintained by John Loomis, last updated 9 July 2014