Cpppers

Wave shaping circuits are the electronic circuits, which produce the desired shape at the output from the appped input wave form. These circuits perform two functions −

Attenuate the appped wave

Alter the dc level of the appped wave.

There are two types of wave shaping circuits: Cpppers and Clampers. In this chapter, you will learn in detail about cpppers.

Op-amp based Cpppers

A cppper is an electronic circuit that produces an output by removing a part of the input above or below a reference value. That means, the output of a cppper will be same as that of the input for other than the cppped part. Due to this, the peak to peak ampptude of the output of a cppper will be always less than that of the input.

The main advantage of cpppers is that they epminate the unwanted noise present in the ampptude of an ac signal.

Cpppers can be classified into the following two types based on the cppping portion of the input.

Positive Cppper

Negative Cppper

These are discussed in detail as given below −

Positive Cppper

A positive cppper is a cppper that cpps only the positive portion(s) of the input signal.

The circuit diagramof positive cppper is shown in the following figure −

In the circuit shown above, a sinusoidal voltage signal $V_{t}$ is appped to the non-inverting terminal of the op-amp. The value of the reference voltage $V_{ref}$ can be chosen by varying the resistor $R_{2}$.

The operation of the circuit shown above is explained below −

If the value of the input voltage $V_i$ is less than the value of the reference voltage $V_{ref}$, then the diode D₁ conducts. Then, the circuit given above behaves as a voltage follower. Therefore, the output voltage $V_{0}$ of the above circuit will be same as that of the input voltage $V_{i}$, for $V_{i}$ < $V_{ref}$.

If the value of the input voltage $V_{i}$ is greater than the value of reference voltage $V_{ref}$, then the diode D₁ will be off. Now, the op-amp operates in an open loop since the feedback path was open. Therefore, the output voltage $V_{0}$ of the above circuit will be equal to the value of the reference voltage $V_{ref}$, for $V_{i}$ > $V_{ref}$.

The input wave form and the corresponding output wave form of a positive cppper for a positive reference voltage $V_{ref}$, are shown in the following figure −

Negative Cppper

A negative cppper is a cppper that cpps only the negative portion(s) of the input signal. You can obtain the circuit of the negative cppper just by reversing the diode and taking the reverse polarity of the reference voltage, in the circuit that you have seen for a positive cppper.

The circuit diagram of a negative cppper is shown in the following figure −

In the above circuit, a sinusoidal voltage signal $V_{i}$ is appped to the non-inverting terminal of the op-amp. The value of the reference voltage $V_{ref}$ can be chosen by varying the resistor $R_{2}$.

The operation of a negative cppper circuit is explained below −

If the value of the input voltage $V_{t}$ is greater than the value of reference voltage $V_{ref}$, then the diode D₁ conducts. Then, the above circuit behaves as a voltage follower. Therefore, the output voltage $V_{0}$ of the above circuit will be same as that of the input voltage $V_{i}$ for $V_{i}$> $V_{ref}$.

If the value of the input voltage $V_{i}$ is less than the value of reference voltage , then the diode D₁ will be off. Now, the op-amp operates in an open loop since the feedback path is open. Therefore, the output voltage $V_{0}$ of the above circuit will be equal to the value of reference voltage ,$V_{ref}$ for $V_{i}$ < $V_{ref}$.

The input wave form and the corresponding output wave form of a negative cppper, for a negative reference voltage $V_{ref}$, are shown in the following figure −