26-09-2013, 03:26 PM
To verify the characteristics of CLIPPERS
INTRODUCTION
A circuit which removes the peak of a waveform is known as a clipper. A negative clipper is
shown in Figure above.
During the positive half cycle of the 5 V peak input, the diode is reversed biased. The diode does
not conduct. It is as if the diode were not there. The positive half cycle is unchanged at the output
V(2) in Figure below. Since the output positive peaks actually overlays the input sinewave V(1),
the input has been shifted upward in the plot for clarity.
During the negative half cycle of sine wave input of Figure above, the diode is forward biased,
that is, conducting. The negative half cycle of the sine wave is shorted out. The negative half
cycle of V(2) would be clipped at 0 V for an ideal diode. The waveform is clipped at -0.7 V due
to the forward voltage drop of the silicon diode. The spice model defaults to 0.7 V unless
parameters in the model statement specify otherwise. Germanium or Schottky diodes clip at
lower voltages.
Closer examination of the negative clipped peak reveals that it follows the input for a slight
period of time while the sine wave is moving toward -0.7 V. The clipping action is only effective
after the input sine wave exceeds -0.7 V. The diode is not conducting for the complete half cycle,
though, during most of it.