Clipper circuit using Diode and its applications

#Technical studies – Study 18

Introduction

A clipper is a circuit that removes positive half cycle, negative half cycle or both half cycles of the input waveform. This type of circuit is useful for wave shaping, voltage limiting applications.

Positive clipper circuit:

Circuit diagram of positive clipper

In this circuit the positive half of the input waveform is clipped. Above diagram shows a positive clipper circuit.

In the above circuit, during positive half cycle of the signal diode is on and there is zero voltage across the output. Practically 0.7 V appears across the output as the diode is conducting. During negative half cycle the diode is off so all the input voltage appears across the output.

Waveforms of positive clipper

The diode used in this circuit is a small signal diode. These types of diodes have a bulk resistance that is mentioned in their data sheets. We have connected a series resistor and a load resistor in the circuit. To design a proper clipper circuit we need to consider the three resistance values. There is a design definition for this – the series resistance should be 100 times greater than the bulk resistance and 100 times lower than the load resistance. This configuration of clipper is called stiff clipper.

Negative clipper circuit:

In this circuit the negative half of the input waveform is clipped. If we reverse the diode as connected in positive clipper we get the negative clipper circuit.

Circuit diagram of negative clipper

In the above circuit, during positive half cycle the diode is off so all the input voltage appears across the output. During negative half cycle the diode is on so there is zero voltage across the output. Practically -0.7 V appears across the output as the diode is conducting in negative direction.

Waveforms of negative clipper

Combination clipper:

In this circuit both the half cycles of the input waveform are clipped. If we combine both positive and negative clipper circuits we get the combination clipper circuit.

Combination clipper circuit

In the above circuit, during positive half cycle of the signal diode D1 is on and D2 is off and there is zero voltage across the output. Practically 0.7 V appears across the output as the diode is conducting. During negative half cycle the diode D1 is off and D2 is on so there is no voltage appears across the output. Practically -0.7 V appears across the output as the diode is conducting in negative direction.

Waveforms of combination clipper

 This circuit can be used as a voltage limiter. This circuit will not allow any voltage above 0.7 V and below -0.7 V. This property of this circuit makes this useful for circuit protection. Sensitive devices can be connected to the output of this circuit for safe operation.

Biased clipper:

The term biased clipper means an external voltage applied to the clipper diode. The purpose of applying the external voltage is to change the clipping level of the clipper circuit.

Biased positive clipper circuit:

 We studied that positive clipper has a clipping level of 0.7 V. The clipping level can be changed by applying an external voltage in series with the diode. This voltage should be less than the input peak voltage.  Now we will get a clipping level equal to 0.7 V + the applied voltage (0.7+V).

Circuit diagram of biased positive clipper
Waveforms of Biased Positive Clipper

Biased negative clipper:

Like positive clipper, negative clipper has a clipping level of -0.7 V. Here we need to connect the external voltage in reverse connection of the positive clipper. This voltage should be less than the input peak voltage.  Now we will get a clipping level equal to -0.7 V + the applied voltage (-0.7-V).

Circuit diagram of biased negative clipper
Waveforms of Biased Negative Clipper

Biased combination clipper:

In this circuit both biased clipper circuits are combined in one circuit. This circuit clips both half cycles of the input wave form to their respective bias levels. As both parts of the sinusoidal wave is clipped, the output looks like a square wave.

Biased combination clipper circuit
Waveforms of biased combination clipper

 

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