STUDY OF DIODE CLIPPING & CLAMPING CIRCUITS

1. Bangladesh University of Engineering & Technology, Dhaka.
Department of Electrical & Electronic Engineering.
Course No: - EEE 212.
Group No: - 02.
Experiment No: - 03.
Name of the Experiment: - STUDY OF DIODE CLIPPING &
CLAMPING
CIRCUITS.
Date of performance: - 13/08/2000. Name: - Mahfuz Quaisar Apu.
Date of submission: - 20/08/2000. Roll: - 9706011.
Department: - EEE.
Section: - A1.
Level: -2, Term: -1.
• REMARKS Session: - 1998-99.
Partner’s Roll: - 9706006-010

2. OBJECTIVE:
To study the application of diodes in different clipping and clamping
circuits.
EQUIPMENTS:
1. One p-n junction Diode (1N4003),
2. Two 5V Zener Diodes (5.6L2)
3. Resistor - 1 KΩ (rated and from color coding)
- 0.984 KΩ (from multimeter),
4. One Capacitor of 10 µF,
5. One Bread Board,
6. One Multimeter,
7. One DC power supply (0 – 50V),
8. One Signal generator (0.1 HZ - 1000 KHZ),
9. Oscilloscope &
10. Chords and wires.
CIRCUIT DIAGRAM:
≈ 1 KΩ
+ +
Ch 1 Vi 10 VP-P (Sinusoidal wave) V0 Ch 2
500 HZ +
VR = 2.5 V _
_ _
Fig 1: Circuit diagram for clipping.

3. 10 µF
+ +
Ch 1 Vi 10 VP-P (Square wave) V0 Ch 2
500 HZ ≈ 1 KΩ
_ _
Fig 2: Circuit diagram for clamping.
≈ 1 KΩ
+ +
D1
Ch 1 Vi 15 VP-P (Sinusoidal wave) V0 Ch 2
500 HZ
D2
_ _
Fig 3: Circuit diagram for double clipping.
REPORT:
1. Clipping:
Clipping is to “clip” of a portion of the input signal without
distorting the remaining part of the alternating waveform. There are a variety of diode
network that can be used as “clippers”. The half-wave rectifier, in our previous
experiment is an example of the simplest form of diode clipper – one resistor and diode,

4. since it passes only the positive (or negative) half-cycle of an alternating waveform and
clips of the other half cycle.
Operation of the circuit in Fig 1:
The circuit has a diode and a dc voltage source in series in output terminal.
In the positive half-cycle of the input voltage, the diode will be at reversed condition at
any value of the input voltage (Vi) less than the dc source voltage (VR). So, at this
condition the diode will act as an open circuit and the output voltage will be equal to the
input voltage i.e. the input waveform will follow the path of the input voltage. But, when
Open Short V
V0 Input
Output
0 Vi 0 t
0 Vi
t
Fig: The piecewise linear transmission characteristics of Fig 1
Vi is equal to or greater than VR the diode will be at forward biased i.e. the diode will be
short circuited. Then the output voltage will hold the value of VR until Vi again becomes
less than VR. After that the output voltage waveform will again follow the path of the
output voltage.

5. Now, in the whole negative half-cycle the diode will be reversed biased i.e. open
circuited. So, the output voltage will be always equal to the input voltage and there will
be no distortion in the wave-shape.
2. The circuit in which the input voltage is Vi = 5Sinωt and the output will be
limited between +2.5V and –3.5V is designed below:
R ≈ 1 KΩ
+ +
D1 D2
Vi = 5Sinωt V0
2.5 V 3.5 V
_ _
Fig:
For the positive half-cycle, both the diode D1 and D2 will be reversed biased for
the values of Vi less than 2.5 volts and the output voltage will be equal to input voltage.
When Vi passes the value of 2.5V the diode D1 is forward biased (short circuited), but the
diode is D2 is still reversed biased. So, the output voltage will hold its value at 2.5V until
Vi is again becomes less than 2.5V i.e. the input positive half-cycle will be clipped at
2.5V.
Vi V0
5V
2.5V
0 0
t t
-3.5V
-5V
Fig: Input and Output waveform of the above circuit.

6. For the negative half-cycle, both the diode D1 and D2 will reversed biased for the
values of Vi greater than -3.5 volts and the output voltage will be equal to input voltage.
When Vi will decrease below -3.5V the diode D2 is forward biased, but the diode is D1 is
still reversed biased. So, the output voltage will hold its value at –3.5V until Vi is again
becomes greater than -3.5V i.e. the input negative half-cycle will be clipped at -3.5V
3. Clamping:
Clamping is to “clamp” a signal to a different dc level, but does not effect
the shape of the waveform. The clamping network must have a capacitor, a diode and a
resistive element. A clamping network can also employ an independent dc supply to
introduce an additional shift. The magnitude of R and C must be chosen such that the
time constant τ = RC is large enough to ensure that the voltage across the capacitor does
not discharge significantly during the interval the diode is non-conducting.
Operation of the circuit in Fig 2:
When the input voltage is positive, the diode is forward biased and the
capacitor charges. During the positive half-cycle of input, the output voltage equals the
zero (for ideal diodes). At this time, the capacitor is charged to Vi.
Vi V0
V
0 t 0 t
-V
-2V
Fig: Input and output voltage waveform.
When the input goes negative, the diode is reverse biased and has no
further effect on the capacitor voltage. Also, the resistance has a very high resistance so
that it cannot discharge the capacitor by very much during the negative portion of the
input waveform. While the input is negative, the output voltage is the sum of the input
and capacitor voltage. Since the polarity of the capacitor voltage is the same as the
(negative) input, the output is a negative voltage that is larger than the peak input level.
∴Output = -Vi – Vi

7. = -2Vi.
4. The output voltage waveform of the circuit of Fig 2 if Vi = 5Sin(2π1000t).
Vi = 5Sin(2π100t)
0 t
-10V
Fig: Output waveform
5. Operation of the circuit in Fig 3:
The circuit in fig 3 has two zener diodes in series, but in opposite polarity.
During the positive half-cycle of the input voltage (Vi) the diode D1 is reversed biased
and the diode D2 is forward biased. As a zener diode acts like a dc voltage source during
reversed biased, the output voltage will first follow the path of the input voltage at every
value less than the diode voltage and the at the diode voltage and above it will hold the
fixed value of the diode D1.
V0
VD1
0 t
VD2
Fig: Output waveform.
In the negative half-cycle of Vi the diode D2 will act like the above and
the negative waveform will again clipped at the fixed D2 voltage. Thus the output voltage
will clipped at the positive half-cycle as well as the negative half-cycle.

8. Discussion:
Clipping and clamping are very widely used diode applications. In this
experiment, we have constructed some clipper and clamper circuits, gave some input
voltage and seen the output of the waveform in the oscilloscope.
But in the waveform and the report there are some points that I want to discuss.
1. During the explanation of the clipper and clamper circuit in the report,
I have assumed that the diodes, we used, were ideal. But in practical level, it is
impossible to make an ideal diode. So, every diode has some internal resistance and a
diode voltage. For this, the waveforms, we have seen in the oscilloscope, were not
exactly the same as I have discussed.
2. The waveform in XY mode for the fig 2 was only two points joining
by a very thin line and was a little bellow of the axes. This was because of the negative
slope (y = mx - c) of the line.