EXP4 - Limiter and Clamper Circuit - Portal

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7 Οκτ 2013 (πριν από 3 χρόνια και 8 μήνες)

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Electronic I

(
DMT 12
1)


Laboratory Module




Exp. 4



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1
-

EXPERIMENT 4

Limiter
and Clamper
Circuit
s


1.

OBJECTIVE:


1.1


To demonstrate the operation of a diode limiter.

1.2


To demonstrate the operation of a diode clamper.



2
.

INTRODUCTION:


PART A : Limiter Circuit


Diode limiters are wave
-
shaping circuit
s: 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 circuit
s

are sometimes called
clippers because of i
ts 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 i
nput signal of a clamper is not changed.


Clamper time constant



















(4.1)


Peak output voltage




(2)

V
out

(peak)

=

V
in

(peak to peak)
-

V
d






(4.2)



3.

COMPONENT AND EQUIPMENT:


PART A : Limiter Circuit


3.1

15
kΩ resistor

3.2

1 kΩ potentiometer

3.3

0


15 V dc power supply

3.4

Signal generator

3.5

Dual trace oscilloscope

3.6

1N4001 silicon rectifier diode

3.7

Breadboard


PART B : Clamper Circuit


3.1

10 kΩ resistor

3.2

10 µF electrolytic capacitor, 25V

3.3

1N400
1 silicon rectifier diode




3.4

Signal generator

3.5

Dual trace oscilloscope

3.6

Breadboard

Electronic I

(
DMT 12
1)


Laboratory Module




Exp. 4



-

2
-

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

Connect the signal generator to the breadboard.

4.1.4

Adjust the signals generator’s output level at 6V peak
-
to
-
peak at a

fr
equency of 200 Hz. (You should see two waveforms similar to
those shown

in Figure 4.2.)




























Figure 4.2

Time
base:

1 ms/division


4.1.5


Sketch the
clipped
waveform, showing the positive and negative peak

values on the data page at the
end of this experiment.

Electronic I

(
DMT 12
1)


Laboratory Module




Exp. 4



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3
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4.2

Negative Limiter Circuit:


4.2.1

Disconnect the signal source from the circuit.

4.2.2

Reverse the polarity of the diode in the cir
cuit, as shown in
Figure 4.3
.
Reconnect the signal to the circuit.
















Figure 4.3 of Negative Limite
r 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
r
emoved, as shown in Figure 4.4
)


Figure 4.4

Time
base:

1ms/division










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DMT 12
1)


Laboratory Module




Exp. 4



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4
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4.3

Positive Biased Clipper Circuit:

4.3.1

Con
nect the circuit of Figure 4.5
.
















Figure 4.5 of Positive Biased Clipper Circuit




4.3.2

Apply power to the breadboard and adjust th
e potentiometer so that the dc
voltage (V
DC
) is + 1.5V.

4.3.3

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
.

4.3.4

Vary the resistance of the 1 kΩ potentiometer from one extreme to the
other. Observe what happened to the clipping level.


4.4

Negative Biased Limiter Circuit:

4.4.1

Reverse the polarities of both the diode and the dc power supply in the
c
ircuit, as shown in Figu
re 4.
6
.
























Figure 4.6 of Negative Biased Limiter Circuit


4.4.2

Adjust the potentiometer so that the dc voltage (V
DC
) is
-
1.5 V.

4.4.3

Connect the signal generator, set at 6V peak
-
to
-
peak, to the breadboard.

4.4.4

Sketch the clipped w
aveform, showing the dc positive and negative peak
values on the data page at the end of this experiment.

4.4.5

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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DMT 12
1)


Laboratory Module




Exp. 4



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5
-

PART B : Clamper Circuit


4.1

Positive Clamper:

4.1.1

Wire the clamper circuit shown in the schematic diagram in Figure 4
.7
.
















F
igure 4.7

Schematic diagram of Positive Clamper circuit


4.1.2 Set oscilloscope to the following approximate settings:


Channels 1 & 2

:

2.0 V/division, dc coupling

Time base


:

0.2 ms

/division


(NOTE: Without any input signal connected to the breadbo
ard, position the two lines on
the oscilloscope’s display so that they are at the same level.)


4.1.3

Connect the signal generator to the breadboard.

4.1.4

Adjust the signal generator’s output level at 5V peak to peak at a frequency
of 1 kHz.

4.1.5

Sketch both the input a
nd the output waveforms, showing the positive and
negative peak values for both on the data page at the end of this
experiment.

4.1.6

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 Fig
ure 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 wh
at 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 t
he peak to peak input
voltage.)









Electronic I

(
DMT 12
1)


Laboratory Module




Exp. 4



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6
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Name

:______________________________
___

Matrix No

: _______________
__

Course

:______________________________
___

Date


: _______________
__


5.

RESULTS:



PART A : Limiter Circuit







Instructor Approval

:

____
________________


Date

:

_____________

Positive limiter (Step
4.
1)

Negative limiter (Step
4.
2)

Positive
-
biased limiter (Step
4.
3)

Negative
-
biased limiter (Step
4.
4)

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DMT 12
1)


Laboratory Module




Exp. 4



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7
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PART B : Clamper Circuit















Instructor Approval

:

____________________


Date

:

_____________

Electronic I

(
DMT 12
1)


Laboratory Module




Exp. 4



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8
-

6. DISCUSSION:


Part A:


Figure
4.8


Assume the Functio
n 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?

Electronic I

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DMT 12
1)


Laboratory Module




Exp. 4



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7.

CONCLUSION:


Explain the difference between a limiting and a clamping circuit.