ECE 201L Circuit Analysis Laboratory
Lab 7

This lab provides further experience with the DAQ and explores the properties of the LM348 operational amplifier and the behavior of diodes.

Attachment: lab7.zip.

Do the following exercises. Report your results by editing the attached 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 8 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, with resistances Rf = 470 kΩ, Rs = 47 kΩ, and RC = 10 kΩ. Calculate the ideal gain and phase shift from the nominal resistance values.

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

      Frequency 500 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 500 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 500 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 500 Hz1 kHz5 kHz10 kHz50 kHz


    Figure 5. Cascaded amplifier

  5. Locate the following diodes in the blue toolboxes: light-emitting diode (LED), 1N4004 rectifier diode, and 1N4148 switching diode.

    Construct the following circuit, shown in Figure 6, using a 100-300 Ω load resistor and a diode. You will need an accurate measurement of the load resistor so use the bench multimeter to make the measurement. Vs is the signal generator. Set the source frequency to 1 kHz and the amplitude to 5 Volts maximum (10 volts peak-to-peak).


    Figure 6. Diode test circuit

    Do the following for each diode:

    1. Examine and capture the resulting input and output signals on the oscilloscope. See example below:

    2. Change the oscilloscope display to XY mode (see instructions at the end of this document) and measure the turn-on voltage of each diode. Capture the resulting oscilloscope images. See example below:

  6. Connect the DAQ to the diode test circuit as shown in Figure 7. Run diode_test.m. Modify the MATLAB script to calculate the effective diode series resistance RS from the slope ρ of the linear part of the VL vs Vin curve, where

    Test each diode and record the turn-on voltage and series resistance.


    Figure 7. DAQ Connections for diode test.

Connecting prototype board to the triple-output power supply


Figure 8. Connecting prototype board to the triple-output power supply.

To use the XY horizontal mode

The XY horizontal mode converts the oscilloscope from a volts-versus-time display to a volts-versus-volts display using two input channels. Channel 1 is the X-axis input, channel 2 is the Y-axis input. You can use various transducers so the display could show strain versus displacement, flow versus pressure, volts versus current, or voltage versus frequency.

  1. Connect the sine wave signal to phase channel 1, and the output sine wave signal to channel 2.

  2. Press the Autoscale key, press the Main/Delayed key, then press the XY softkey.

  3. Center the signal on the display with the channel 1 and 2 position () knobs. Use the channel 1 and 2 volts/div knobs and the channel 1 and 2 Vernier softkeys to expand the signal for convenient viewing.

Data Acquisition Board Pinout

Maintained by John Loomis, last updated 3 July 2010