III.
Zener Circuits
In this lab we will look at several Zener circuits covered in class. You may wish to use the same Zener
diode as used in Lab 1 so that you know the diode turn-on voltage and the Zener breakdown voltage.
III.A.Pre-Lab
In this lab you will be measuring several waveforms versus time and several transfer characteristics. All
of the measurements you will be making can be simulated with PSpice. Read through this lab and identify all the
required plots. Use PSpice to obtain the same plots that you will measure. Paste these plots in your notebook and
compare them to the measured plots when you make the measurements.
For each measurement your notebook should have a PSpice plot and a scope trace. Compare the plots and
make any comments or observations you feel are important.
III.B.Zener Diode Clipping Circuit 1
Wire the circuit of Figure III-2. Let Vs be a 1 kHz triangle wave with an amplitude of 10 V. Obtain a
scope plot of Vo versus time and Vs versus time. Make sure you record all necessary scope settings. Make any
observations such as how the diode voltage drop affects Vo . Compare this plot to your PSpice plot.
Using the procedure developed in Lab 2 for observing transfer characteristics, observe the transfer
function of this circuit, Vo versus Vs . To do this you will need to measure Vs with Channel B and Vs with
Channel A. Obtain a print out of the transfer curve.
III.C.Zener Diode Clipping Circuit 2
Wire the circuit of Figure III-1. Let Vs be a 1 kHz triangle wave with an amplitude of 10 V. Obtain a
scope plot of Vo versus time and Vs versus time. Make sure you record all necessary scope settings. Make any
observations such as how the diode voltage drop affects Vo . Compare this plot to your PSpice plot.
Observe the transfer function of this circuit, Vo versus Vs . To do this you will need to measure Vs with
Channel B and Vs with Channel A. Obtain a print out of the transfer curve.
III.D.Symmetrical Zener Diode Clipping Circuit
Wire the circuit of Figure III-3. Let Vs be a 1 kHz triangle wave with an amplitude of 10 V. Obtain a
scope plot of Vo versus time and Vs versus time. Make sure you record all necessary scope settings. Make any
Figure III-2: Zener diode clipping circuit.
EE 349
Figure III-1 Zener diode clipping circuit2.
III-1
Lab 3
observations such as how the diode voltage drop affects Vo . Compare this plot to your PSpice plot.
Observe the transfer function of this circuit, Vo versus Vs . To do this you will need to measure Vs with
Channel B and Vs with Channel A. Obtain a print out of the transfer curve.
III.E.Zener Diode Dead Zone Clipping Circuit
The circuit of Figure III-4 is called a ``Dead Zone'' clipping circuit. Analysis of this circuit will show that
Vo will be zero unless the magnitude of the input is equal to the Zener break down voltage plus a diode voltage
drop.
Wire the circuit of Figure III-4. Let Vs be a 1 kHz triangle wave with an amplitude of 10 V. Obtain a
scope plot of Vo versus time and Vs versus time. Make sure you record all necessary scope settings. Make any
observations such as how the diode voltage drop affects Vo .
Compare this plot to your PSpice plot.
Observe the transfer function of this circuit, Vo versus Vs .
To do this you will need to measure Vs with Channel B and Vs
with Channel A. Obtain a print out of the transfer curve.
III.F.Lab 3 Check Sheet
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EE 349
Zener Diode Clipping Circuit 1
1.
PSpice plot of Vs and Vo versus time.
2.
Measured plot of Vs and Vo versus time.
3.
PSpice transfer characteristic.
4.
Scope display of transfer characteristic.
Zener Diode Clipping Circuit 2
1.
PSpice plot of Vs and Vo versus time.
2.
Measured plot of Vs and Vo versus time.
3.
PSpice transfer characteristic.
4.
Scope display of transfer characteristic.
Symmetrical Zener Diode Clipping Circuit
1.
PSpice plot of Vs and Vo versus time.
2.
Measured plot of Vs and Vo versus time.
3.
PSpice transfer characteristic.
4.
Scope display of transfer characteristic.
Zener Diode "Dead Zone" Clipping Circuit
1.
PSpice plot of Vs and Vo versus time.
2.
Measured plot of Vs and Vo versus time.
3.
PSpice transfer characteristic.
4.
Scope display of transfer characteristic.
III-2
Figure III-3: Symmetrical Zener diode
clipping circuit.
Figure III-4: Dead zone clipping
circuit.
Lab 3