# Clippers

## Clippers

• Clipper circuit which control the shape of output waveform by removing and clipping a portion of applied wave is known as clipping circuit.

Clippers

## Positive Clipper

• A circuit that removes positive parts of the input signal can be formed by using an op-amp with a rectifier diode.
• The clipping level is determined by the reference voltage Vref, which should less than the i/p range of the op-amp (Vref < Vin).
• The Output voltage has the portions of the positive half cycles above Vref clipped off.

Positive Clippers

## Working of Positive Clipper

• During the positive half cycle of the input, the diode D1 conducts only until Vin = Vref.
• This happens because when Vin < Vref, the output volts V0 of the op-amp becomes negative to device D1 into conduction when D1 conducts it closes feedback loop and op-amp operates as a voltage follower. (i.e.) Output V0 follows input until Vin = Vref.
• When Vin > Vref => the V0 becomes +ve to derive D1 into off. It opens the feedback loop and op- amp operates open loop.
• When Vin drops below Vref (Vin < Vref) the o/p of the op-amp V0 again becomes –ve to device D1 into conduction. It closes the feedback path. (o/p follows the i/p). Thus diode D1 is on for Vin < Vref (o/p follows the i/p) and D1 is off for Vin > Vref.

## Negative Clipper

• The positive clipper is converted into a negative clipper by simply reversing diode D1 and changing the polarity of Vref voltage.
• The negative clipper clips off the –Ve parts of the input signal below the reference voltage.

## Working of Negative Clipper

• Diode D1 conducts -> when Vin > -Vref and therefore during this period o/p volt V0 follows the i/p volt Vin. The –Ve portion of the output volt below –Vref is clipped off because (D1 is off) Vin < -Vref.
• If –Vref is changed to –Vref by connecting the potentiometer Rp to the +Vcc, the V0 below + Vref will be clipped off. The diode D1 must be on for Vin > Vref and off for Vin.

## Single End Clipper

• The positive terminal of the battery connected to the diodes cathode therefore diode conducts when input voltage reaches at the level of 4.7 volt.
• When diode is conducting there will be no current in RL and no voltage will drop across RL. So that all the input voltage above this level will be clipped off at the output.

Single End Clipper

## Double Diode Clipper

• A Circuit that can be used to limit the peaks of both half cycles of an A.C. input signal is called double end clipper.
• This circuit contains a shunt positive clipper with positive bias and shunt negative clipper with negative bias.

Double Diode Clipper