ECE 323L Basic Electronic Circuits Laboratory

Lab 12

 

 

Names:

 

 

 

Do the following exercises. Report your results by editing this Word document and submitting it in WebCT.

 

This laboratory explores some circuits using diodes.

 

  1. Construct the following circuit, shown in Figure 1, using a 100 W load resistor and a diode. You will be testing three different diodes: a 1N4004 rectifier diode, a 1N4148 switching diode, and a red light-emitting diode (LED).

 

 

Figure 1.  Diode test circuit

 

Set the source frequency to 1 kHz and the amplitude to 5 Volts maximum (10 volts peak-to-peak). 

 

a)      Measure the maximum source voltage and maximum load voltage for each diode. Insert an oscilloscope image for the 1N4148 showing measured values of the maximum voltage levels for input and load voltages.

 

Diode

Max VS

Max VL

1N4148

 

 

1N4004

 

 

Red LED

 

 

 

 

b)      Change the oscilloscope display to XY mode (see instructions at the end of this document) and measure the turn-on voltage of each diode. Insert an oscilloscope image showing XY mode for the 1N4148 diode.

 

Diode

Turn-on

1N4148

 

1N4004

 

Red LED

 

 

c)      Change the oscilloscope mode to normal (time mode). Change the source waveform to square wave and the frequency to 20 kHz.  Insert an oscilloscope image showing the results.  Measure the reverse recovery time for the 1N4004 diode.

 

 

Diode

Recovery time

1N4004

 

 

 

  1. Construct the full-wave bridge rectifier shown in Figure 2.  Use a 1500 W resistor for the load. Use 1N4004 diodes.

 

 

 

 

Figure 2. Full-wave diode-bridge rectifier.

 

 

 

a)      Measure source voltage on oscilloscope with probes between A and B. Measure load voltage with probes between C and D. Do not attempt to measure both signals on the oscilloscope at the same time, the oscilloscope channels share a common ground and trying to make simultaneous measurements will introduce ground loop problems.

Set the frequency of the source to 50 Hz and the amplitude to 10 volts peak-to-peak. Attach oscilloscope images of the source voltage and the load voltage to the report, showing the maximum voltage in each signal.

 

 

Diode

Max VS

Max VL

1N4004

 

 

Red LED

 

 

 

 

b)      Add a 100-mF filter capacitor to the rectifier as shown in Figure 3.

 

 

Figure 3. Rectifier with filter capacitor.

 

 

Measure the maximum load voltage and ripple (peak-to-peak voltage).  Insert an oscilloscope image showing these measurements

 

Diode

Max VL

ripple

1N4004

 

 

 

 

  1. Change the diodes in Figure 2 to LEDs. Reduce the input frequency to 1 Hz. Observe the pattern of lights and demonstrate to the lab assistant. Measure the maximum source voltage and maximum load voltage.

 

 

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.

 

 

 

maintained by John Loomis, updated 24 March 2008