Positive clipper is a clipper circuit that clips positive portion of the waveform above a certain positive reference voltage.
Figure below shows the circuit diagram of a positive clipper circuit.
Positive clipper circuit
During positive half cycles, for input voltages less than or equal to reference voltage (VREF), the opamp output goes to positive saturation and diode (D1) is reverse-biased with the result that the input appears as such at the output. When the input voltage exceeds the reference voltage, the opamp output goes to negative saturation and the diode gets forward-biased. The output gets shorted to inverting input and the output is clamped to VREF. The input and output waveforms are shown in figure below.
Input and output waveforms for a positive clipper
If the polarity of the reference voltage is negative, clipping occurs below zero voltage. The input and the output waveforms are shown in the figure below.
Input and output waveforms for a positive clipper with negative reference voltage
Negative clipper is a clipper circuit that clips negative half portion of the waveform below a certain reference voltage.
Figure below shows a negative clipper circuit.
Negative clipper circuit
During positive half cycles and also for input voltages less negative or equal to (–VREF), diode (D1) is reverse-biased. The input appears as such at the output. For input voltages more negative than –VREF, diode (D1) is forward-biased and the output gets clamped at the reference voltage. The input and output waveforms are shown in figure below.
Input and the output waveforms for a negative clipper circuit
When the polarity of the reference voltage is negative, clipping occurs above zero voltage. The input and the output waveforms are shown in figure below.
Input and output waveforms for a negative clipper with negative reference voltage