Clipping above Reference Voltage VR

Series Clippers : Part4
       The output of the clipper can be adjusted as per the requirement by adding an additional voltage source in series with the load resistance as shown in the Fig. 1.

Fig. 1   Clipping above V_R

       The diode D is an ideal diode and hence there is no drop across it when it is forward biased. Thus when forward biased, it acts as a short circuit while when reverse biased it acts as open circuit.

Operation :

       When V_i is less than V_R, the diode becomes forward biased and the circuit can be reduced as shown in the Fig. 2(a). In this case the output voltage V_o is equal to input voltage V_i. When V_i is greater than V_R, the diode is reverse biased and circuit gets reduced to, as shown in the Fig. 2(b). No current can flow in the circuit as circuit is open and hence output voltage V_o is equal to V_R.

Fig.  2

       The input and output waveforms for such a clipper are shown in the Fig. 3.

Fig. 3  Waveforms for clipping above V_R

Note : It can be seen that the portion of the input waveform above V_R gets clipped off. The level of  V_R can be adjusted as per the requirement by selecting proper battery voltage.

       Mathematically this can be expressed as,

       This mathematical representation helps us to sketch the transfer characteristics of the clipper circuit. The transfer characteristics is the graph of output voltage V_o against input voltage V_i. The above equations are called the transfer characteristics is shown in the Fig. 4.

Fig. 4  Transfer characteristics

       For the portion till V_i < V_R, the graph is straight line. This region is called the transmission region as it transmits V_i at the output as it is. While the portion for V_i >V_R, the output is constant. This region is called clipping region.

Sponsored links :