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Electronic I (DMT 121)
Laboratory Module
Exp. 4
EXPERIMENT 4
Limiter and Clamper Circuits
1.
OBJECTIVE:
1.1
1.2
2.
To demonstrate the operation of a diode limiter.
To demonstrate the operation of a diode clamper.
INTRODUCTION:
PART A : Limiter Circuit
Diode limiters are wave-shaping circuits: can be used to prevent signal voltages from going
above or below certain levels. The limiting level may be either equal to the diode’s barrier
potential or made variable with a dc source voltage. These circuits are sometimes called
clippers because of its clipping capability.
PART B : Clamper Circuit
The clamper also falls into the wave shaping circuit group. Since it adds a dc level to the input
waveform, it is often referred to as a dc restorer. However, unlike that of the clipper, the
shape of the input signal of a clamper is not changed.
Clamper time constant
10 R L C  Tinput
Peak output voltage
(2) Vout (peak)
3.
(4.1)
=
Vin (peak to peak) - Vd
COMPONENT AND EQUIPMENT:
PART A : Limiter Circuit
3.1
3.2
3.3
3.4
3.5
3.6
3.7
15 kΩ resistor
1 kΩ potentiometer
0 – 15 V dc power supply
Signal generator
Dual trace oscilloscope
1N4001 silicon rectifier diode
Breadboard
PART B : Clamper Circuit
3.1
3.2
3.3
3.4
3.5
3.6
10 kΩ resistor
10 µF electrolytic capacitor, 25V
1N4001 silicon rectifier diode
Signal generator
Dual trace oscilloscope
Breadboard
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(4.2)
Electronic I (DMT 121)
4.
Laboratory Module
Exp. 4
PROCEDURE:
PART A : Limiter Circuit
4.1
Positive Limiter Circuit:
4.1.1 Wire the limiter circuit shown in the schematic diagram in Figure 4.1.
Figure 4.1 of Positive Limiter Circuit
4.1.2 Set oscilloscope to the following settings:
Channels 1 & 2
:
1 V/division, dc coupling
Time base
:
1 ms/division
(NOTE: Without any input signal connected to the breadboard, position the two lines on
the oscilloscope’s display so that they are at the same level (that is, zero volts)
centered vertically on the display.)
4.1.3
4.1.4
Connect the signal generator to the breadboard.
Adjust the signals generator’s output level at 6V peak-to-peak at a
frequency of 200 Hz. (You should see two waveforms similar to those shown
in Figure 4.2.)
Figure 4.2
4.1.5
Time base: 1 ms/division
Sketch the clipped waveform, showing the positive and negative peak
values on the data page at the end of this experiment.
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Electronic I (DMT 121)
4.2
Laboratory Module
Exp. 4
Negative Limiter Circuit:
4.2.1
4.2.2
Disconnect the signal source from the circuit.
Reverse the polarity of the diode in the circuit, as shown in Figure 4.3.
Reconnect the signal to the circuit.
Figure 4.3 of Negative Limiter Circuit
4.2.3
Sketch the clipped waveform, showing the positive and negative peak values
on the data page at the end of this experiment.
(NOTE: The behavior is opposite that if the positive limiter. The waveform has all
negative peaks of the input signal removed, as shown in Figure 4.4)
Figure 4.4 Time base: 1ms/division
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Electronic I (DMT 121)
4.3
Laboratory Module
Exp. 4
Positive Biased Clipper Circuit:
4.3.1 Connect the circuit of Figure 4.5.
Figure 4.5 of Positive Biased Clipper Circuit
4.3.2
4.3.3
4.3.4
4.4
Apply power to the breadboard and adjust the potentiometer so that the dc
voltage (VDC) is + 1.5V.
Connect the signal generator, set at 6 V peak-to-peak, to the breadboard.
Sketch the clipped waveform, showing the dc positive and negative peak
values on the data page at the end of this experiment.
Vary the resistance of the 1 kΩ potentiometer from one extreme to the
other. Observe what happened to the clipping level.
Negative Biased Limiter Circuit:
4.4.1 Reverse the polarities of both the diode and the dc power supply in the
circuit, as shown in Figure 4.6.
Figure 4.6 of Negative Biased Limiter Circuit
4.4.2
4.4.3
4.4.4
4.4.5
Adjust the potentiometer so that the dc voltage (VDC) is -1.5 V.
Connect the signal generator, set at 6V peak-to-peak, to the breadboard.
Sketch the clipped waveform, showing the dc positive and negative peak
values on the data page at the end of this experiment.
Vary the resistance of the 1 kΩ potentiometer from one extreme to the
other. Observe what happened to the clipping level.
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Electronic I (DMT 121)
Laboratory Module
Exp. 4
PART B : Clamper Circuit
4.1
Positive Clamper:
4.1.1 Wire the clamper circuit shown in the schematic diagram in Figure 4.7.
Figure 4.7
4.1.2
Schematic diagram of Positive Clamper circuit
Set oscilloscope to the following approximate settings:
Channels 1 & 2
Time base
:
:
2.0 V/division, dc coupling
0.2 ms /division
(NOTE: Without any input signal connected to the breadboard, position the two lines on
the oscilloscope’s display so that they are at the same level.)
4.1.3
4.1.4
4.1.5
4.1.6
Connect the signal generator to the breadboard.
Adjust the signal generator’s output level at 5V peak to peak at a frequency
of 1 kHz.
Sketch both the input and the output waveforms, showing the positive and
negative peak values for both on the data page at the end of this
experiment.
Increase the peak to peak input voltage. Observe the waveforms.
4.2 Negative Clamper:
4.2.1 Reverse the polarity of the diode in the Figure 4.7, and repeat Step 4.1.
Observe what happens.
4.2.2 Sketch both the input and the output waveforms, showing the positive and
negative peak values for both on the data page at the end of this experiment.
4.2.3 Increase the peak to peak input voltage. Observe what happens.
(NOTE: You should see that the peak to peak output voltage increases, its positive peak
remains clamped at the same positive voltage level measured before. You should find that
the negative peak output voltage is again approximately equal to the peak to peak input
voltage.)
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Electronic I (DMT 121)
Name
Laboratory Module
Exp. 4
:_________________________________
Course :_________________________________
5.
Matrix No
: _________________
Date
: _________________
RESULTS:
PART A : Limiter Circuit
Negative limiter (Step 4.2)
Positive limiter (Step 4.1)
Positive-biased limiter (Step 4.3)
Instructor Approval
:
Negative-biased limiter (Step 4.4)
____________________
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Date :
_____________
Electronic I (DMT 121)
Laboratory Module
Exp. 4
PART B : Clamper Circuit
Instructor Approval
:
____________________
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Date
:
_____________
Electronic I (DMT 121)
6.
Laboratory Module
Exp. 4
DISCUSSION:
Part A:
Figure 4.8
Assume the Function Generator is set for a 6 Vpp sine wave at 1.0 kHz. Sketch waveform you
would expect to see on the oscilloscope screen.
Part B:
Figure 4.9
An oscilloscope is connected to the circuit from Figure 4.9 as shown. Is the circuit working
correctly? If not, what is the likely problem?
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Electronic I (DMT 121)
7.
Laboratory Module
Exp. 4
CONCLUSION:
Explain the difference between a limiting and a clamping circuit.
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