Course Title : Electronic Devices and circuits: MSC 1st PHY
9 & Onwards
Instructor :sir javed iqbal
Name: syeda Anmol Rida Registration Number: uw-20-
phy-Msc-007
Program: msc physics smster: 1st
ELECTRONIC DEVICES & CIRCUITS LAB
Aim:
To design a clamper circuit Design.
Components required:
Function generator, CRO, Regulated Power supply, resistor,
diode, connecting wires.
Vlab Specifications Taken:
clamper circuit design has been implemented on the virtual
breadboard using following specifications:
· Power Supply: +10v and -10v
· Function generator: Selected wave with following
specifications:
Frequency = 1KHz.
Amplitude: 5V
Duty cycle = 50%
· Resistor R1: 1.39K
Theory:
Clamper is a circuit that "clamps" a signal to a different dc level.
A clamping network must have a capacitor, a diode and a
resistive element. The magnitude R and C must be chosen such
that the time constant RC is large enough to ensure that the
voltage across the capacitor does not discharge significantly
during the interval the diode is non- conducting.
Positive Clamper
The circuit for a positive clamper is shown in the figure. During
the negative half cycle of the input signal, the diode conducts
and acts like a short circuit. The output voltage V o = 0V. The
capacitor is charged to the peak value of input voltage V m. and
it behaves like a battery. During the positive half of the input
signal, the diode does not conduct and
If the circuit pushes the signal upwards then the circuit is said
to be a positive clamper. When the signal is pushed upwards,
the negative peak of the signal meets the zero level.
On the other hand, if the circuit pushes the signal downwards
then the circuit is said to be a negative clamper. When the
signal is pushed downwards, the positive peak of the signal
meets the zero level.
The construction of the clamper circuit is almost similar to the
clipper circuit. The only difference is the clamper circuit
contains an extra element called capacitor. A capacitor is used
to provide a dc offset (dc level) from the stored charge.
During positive half cycle:
During the positive half cycle of the input AC signal, the diode is
forward biased and hence no signal appears at the output. In
forward biased condition, the diode allows electric current
through it. This current will flows to the capacitor and charges it
to the peak value of input voltage in inverse polarity -Vm. As
input current or voltage decreases after attaining its maximum
value Vm, the capacitor holds the charge until the diode remains
forward biased.
During negative half cycle:
During the negative half cycle of the input AC signal, the diode
is reverse biased and hence the signal appears at the output. In
reverse biased condition, the diode does not allow electric
current through it. So the input current directly flows towards
the output.
When the negative half cycle begins, the diode is in the non-
conducting state and the charge stored in the capacitor is
discharged (released). Therefore, the voltage appeared at the
output is equal to the sum of the voltage stored in the capacitor
(-Vm) and the input voltage (-Vm) {I.e. Vo = -Vm- Vm = -2Vm} which
have the same polarity with each other. As a result, the signal
shifted downwards
• Biased clampers
Sometimes an additional shift of DC level is needed. In such
cases, biased clampers are used. The working principle of the
biased clampers is almost similar to the unbiased clampers. The
only difference is an extra element called DC battery is
introduced in biased clampers.
Positive clamper with positive bias
If positive biasing is applied to the clamper then it is said to be a
positive clamper with positive bias. The positive clamper with
positive bias is made up of an AC voltage source, capacitor,
diode, resistor, and dc battery.
During positive half cycle:
During the positive half cycle, the battery voltage forward
biases the diode when the input supply voltage is less than the
battery voltage. This current or voltage will flows to the
capacitor and charges it.
When the input supply voltage becomes greater than the
battery voltage then the diode stops allowing electric current
through it because the diode becomes reverse biased.
During negative half cycle:
During the negative half cycle, the diode is forward biased by
both input supply voltage and battery voltage. So the diode
allows electric current. This current will flows to the capacitor
and charges it.
Positive clamper with negative bias
During negative half cycle:
During the negative half cycle, the battery voltage reverse
biases the diode when the input supply voltage is less than the
battery voltage. As a result, the signal appears at the output.
When the input supply voltage becomes greater than the
battery voltage, the diode is forward biased by the input supply
voltage and hence allows electric current through it. This
current will flows to the capacitor and charges it.
During positive half cycle:
During the positive half cycle, the diode is reverse biased by
both input supply voltage and the battery voltage. As a result,
the signal appears at the output. The signal appeared at the
output is equal to the sum of the input voltage and capacitor
voltage.
Negative clamper with positive bias
During positive half cycle:
During the positive half cycle, the battery voltage reverse biases
the diode when the input supply voltage is less than the battery
voltage. When the input supply voltage becomes greater than
the battery voltage, the diode is forward biased by the input
supply voltage and hence allows electric current through it. This
current will flows to the capacitor and charges it.
During negative half cycle:
During the negative half cycle, the diode is reverse biased by
both input supply voltage and battery voltage. As a result, the
signal appears at the output.
Negative clamper with negative bias
During positive half cycle:
During the positive half cycle, the diode is forward biased by
both input supply voltage and battery voltage. As a result,
current flows through the capacitor and charges it.
During negative half cycle:
During the negative half cycle, the battery voltage forward
biases the diode when the input supply voltage is less than the
battery voltage. When the input supply voltage becomes
greater than the battery voltage, the diode is reverse biased by
the input supply voltage and hence signal appears at the
output.
Procedure:
1. Connect the circuit as shown in the circuit diagram.
2. Give the input signal as specified.
3. Switch on the power supply.
4. Note down the value of AC and DC voltages from the CRO
5. Draw the necessary waveforms on the graph sheet.
Observations:
1. Observe the output waveform from CRO.
2. Measure the value of AC and DC voltages of the output and
the input waveforms from the CRO.
3. Observe and compare the maximum and minimum vltages
of the input and output waveforms.
