2 DIODE CLIPPING and CLAMPING CIRCUITS

Objectives

• Understanding the operating principle of diode clipping circuit

• Understanding the operating principle of clamping circuit

• Understanding the waveform change of diode clipping and clamping circuits

when the bias is applied

Basic Description

As you know, diodes can be used as switches depending on the biasing type,

reverse of forward. The clipping circuit, also referred to as clipper, clips off some of

the portions of the input signal and uses the clipped signal as the output signal. The

clamping circuit or clamper keeps the amplitude of the output signal same as that of

the input signal except that the D.C. level (offset) has been changed. The clamper

through which the input waveform shifts to positive direction is called positive

clamper, otherwise, is called negative clamper.

Diode Clipping Circuit

In these type of circuits, the diode is connected between the input and output

voltage terminals

the negative cycle of the input voltage can be clipped of by

this type of series clippers. Reverse of the diode pins yields to a positive cycle

clipping circuit as shown in Fig. 2.3.

Previous circuits clip the values larger or smaller than zero voltage. This

voltage, technically called “threshold voltage” and can be changed to a desired value

by inserting a D.C. voltage source. This is achieved in two different ways.

In the first type, the voltage source of Em ( positive or negative) is connected

through output terminals as in Fig. 2.4. Depending on the diode connection (normalor reverse), the values smaller (Fig.2.4.a) or greater (Fig.2.4.b) than Em is clipped

and assigned as Em. .

OUTPUT

Clamper Circuits

Clamper Circuits, or briefly clampers are used to change the D.C. level of a

signal to a desired value.( Fig 2.8 ).

CIRCUIT DIAGRAM:

Being different from clippers, clamping circuits uses a capacitor and a diode

connection. When diode is in its on state, the output voltage equals to diode drop

voltage (ideally zero) plus the voltage source, if any. Now let us examine the

clamping process for the circuit

The resulting signal after a complete cycle is shown below.

By this process, the input signal is shifted to negative D.C. value (its maximum

value is ideally zero) without any change in its amplitude ideally.

There exist again modified versions of this circuit in which a threshold value is

inserted for clamping. Following figures illustrate these modifications and resulting

outputs.