Clippers:

In the clipper circuits, discussed so far, diodes are assumed to be ideal device. If third approximation circuit of diode is used, the transfer characteristics of the clipper circuits will be modified.

Clipper Circuit 4:

Consider the clipper circuit shown in fig. 1 to clip the input signal above reference voltage

Fig. 1	Fig. 2

When v_i < (V_R+ V_r), diode D is reverse biased and therefore, v_o= v_i.

and when v_i > ( V_R + V_r ), diode D is forward biased and conducts. The equivalent circuit, in this case is shown in fig. 2.

The current i in the circuit is given by The transfer characteristic of the circuit is shown in fig. 3.

Fig. 3

  Clipper Circuit 5:

Consider the clipper circuit shown in fig. 4, which clips the input signal below the reference level (V_R).

If v_i > (V_R – V_r), diode D is reverse biased, thus v_O = v_i and when v_i < (v_R -V_r), D condcuts and the equivalent circuit becomes as shown in fig. 5.

Fig. 4	Fig. 5
Therefore, The transfer characteristic of the circuit is shown in fig. 6.	Fig. 6

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