DIODE CLIPPER - Websmemberfiles.freewebs.com/41/36/96773641/documents/DIODE...• Clipping circuit...
Transcript of DIODE CLIPPER - Websmemberfiles.freewebs.com/41/36/96773641/documents/DIODE...• Clipping circuit...
DIODE CLIPPER
A device which removes the peak of a waveform is known as a Clipper
Voltage clipping diagram
• Clipping circuit is a wave-shaping circuit, and is used to either remove or clip a portion of the applied wave in order to control the shape of the output waveform
• Clipping Circuits are also called as Slicers, amplitude selectors or limiter
Clipping circuit
A clipping circuit consists of
• Resistor
• Junction diode
• A battery
• Load resistance
• According to level of clipping the clippers may be
Positive clippers
Negative clippers
Biased clippers
Combination clippers
• There are two general categories of clippers: series parallel (shunt)
Types of clippers
• The positive half cycles of the input voltage will be removed
• During the positive half cycle of the input waveform, the diode ‘D’ is reverse biased, Thus causes the positive half cycle to be clipped off.
• During the negative half cycle of the input, the diode is forward biased and so the negative half cycle appears across the output.
Positive Diode Clipper
Negative Diode Clipper
The negative clipping circuit is almost same as the positive
clipping circuit, If the diode is reconnected with reversed
polarity, the circuits will become for a negative series
clipper and negative shunt clipper respectively figure (a)
and (b).
In a practical diode, the breakdown voltage will exist (0.7 V for silicon and
0.3 V for Germanium). When this is taken into account, the output wave-
forms for positive and negative clippers will be of the shape shown in the
figure below.
Practical diode Clipper
Biased Positive Clipper and Biased Negative Clipper
• When a small portion of positive or negative half cycles of the signal voltage is to be removed.
• When a small portion of the negative half cycle is to be removed, clipper is called biased negative clipper
• When a small portion of the positive half cycle is to be removed,
clipper is called biased negative clipper
a
b
Working of Biasing Clipper
In a biased clipper, when the input signal voltage is positive, the diode ‘D’ is reverse-
biased. Thus the entire positive half cycle appears across the load, as illustrated by
output waveform [figure (a)]. When the input signal voltage is negative but does not
exceed battery the voltage ‘V’, the diode ‘D’ remains reverse-biased and most of the
input voltage appears across the output. When during the negative half cycle of input
signal, the signal voltage becomes more than the battery voltage V, the diode D is
forward biased and so conducts heavily. The output voltage is equal to ‘- V’ and stays at ‘-
V’ as long as the magnitude of the input signal voltage is greater than the magnitude of
the battery voltage, ‘V’. Thus a biased negative clipper removes input voltage when the
input signal voltage becomes greater than the battery voltage. Clipping can be changed
by reversing the battery and diode connections, as illustrated in figure (b).
When a portion of both positive and negative of each half cycle of the input
voltage is to be clipped (or removed), combination clipper is employed
combination clipper
For positive input voltage signal when input voltage exceeds battery voltage ‘+
V1‘ diode D1 conducts heavily while diode ‘D2‘ is reversed biased and so voltage
‘+ V1‘ appears across the output. This output voltage ‘+ V1‘ stays as long as. the
input signal voltage exceeds ‘+ V1‘. On the other hand for the negative input
voltage signal, the diode ‘D1‘ remains reverse biased and diode ‘D2‘ conducts
heavily only when input voltage exceeds battery voltage ‘V2‘ in magnitude.
Thus during the negative half cycle the output stays at ‘- V2‘ so long as the
input signal voltage is greater than ‘-V2‘.
Working of combination clipper
CLAMPERS
COMPONETS OF CLAMPING CIRCUIT
• Capacitor
• Junction diode
• Resistance
CLAMPING CIRCUIT
• A clamping circuit is used to place either the positive or
negative peak of a signal at a desired level
• A clamp circuit adds the positive or negative dc component to
the input signal so as to push it either on the positive side, as
illustrated in figure (a) or on the negative side, as illustrated in
figure (b)
CLAMPING CIRCUIT
POSITIVE CLAMPER
• The signal is pushed upward by the circuit
NEGATIVE CLAMPER
• The signal is pushed downward by the circuit
A circuit that shifts the original signal in a vertical downward direction, as shown
in the figure above. The diode D will be forward biased and the capacitor C is
charged with the polarity shown, when an input signal is applied. During the
positive half cycle of input, the output voltage will be equal to the barrier
potential of the diode, V0 and the capacitor is charged to (V – VQ). During the
negative half cycle, the diode becomes reverse-biased and acts as an open-
circuit. Thus, there will be no effect on the capacitor voltage. The resistance R,
being of very high value, cannot discharge C a lot during the negative portion of
the input waveform. Thus during negative input, the output voltage will be the
sum of the input voltage and the capacitor voltage and is equal to – V – (V — V0)
or – (2 V – V0). The value of the peak-to-peak output will be the difference of the
negative and positive peak voltage levels is equal to V0-[-(2V-V0)] or 2 V.
Negative clamper circuit
The figure shown below can me modified into a positive clamping
circuit by reconnecting the diode with reversed polarity. The positive
clamping circuit moves the original signal in a vertical upward
direction. A positive clamping circuit is shown in the figure below. It
contains a diode D and a capacitor C as are contained in a negative
clamper. The only difference in the circuit is that the polarity of the
diode is reversed. The remaining explanation regarding the working of
the circuit is the same as it is explained for the negative clamper.
Positive clamper circuit
• The shape of the waveform will be the same, but its level is
shifted either upward or downward
• There will be a change in the peak and average values of the
waveform
• The values of the resistor R and capacitor C affect the
waveform.
• We have a positive dc clamper and when the diode points
downward, the circuit is a negative dc clamper.
IMPORTANT POINTS