Basic Parallel Clipper with Negative Clipping

Parallel Clippers : Part3

       Note : The negative clipping with basic parallel clipper can be achieved by reversing the direction of diode.

       When V_in  is positive then the diode is reversed biased and acts as an open circuit. Thus the output voltage V_o is same as V_in  for R₁ < < R_L. Hence the positive half cycle of  V_in gets reproduced at the output. This is shown in the Fig. 1.

Fig. 1  Basic parallel clipper

Fig. 2  Basic parallel clipper ( Negative clipping)

       The magnitude of the output voltage is,

       Consider the negative half cycle of V_in. As V_in decreases below zero and becomes -0.7 V, the diode becomes forward biased and acts conducting. As long as V_in < -0.7 V, the diode remains ON and drop across it is cut-in voltage V_γ = 0.7 V, with polarities as shown in the Fig. 2(a).

Note : As diode and R_L are in parallel, the output voltage is equal to the drop across diode i.e. 0.7 V in opposite direction.

.^..                   V_o   = -0.7 V                           for V_in < -0.7V

       Thus the entire negative half cycle gets clipped off, as shown in the Fig. 2(b).

Fig.3  Basic parallel clipper ( Negative clipping)

       The overall input-output waveforms can be shown as in the Fig. 3. The Fig.4(a) shows the waveforms with piecewise model of diode while the Fig. 4(b) shows the waveforms with an ideal diode approximation with V_γ = 0 V.

Fig. 4

Transfer characteristics :

       The transfer characteristics equations are,

      The transfer characteristics are shown in the Fig. 5.

Fig. 5  Transfer characteristics