Electronic Circuits - Negative Cppper Circuits

The Cppper circuit that is intended to attenuate negative portions of the input signal can be termed as a Negative Cppper. Among the negative diode cppper circuits, we have the following types.

Negative Series Cppper

Negative Series Cppper with positive $V_{r}$ (reference voltage)

Negative Series Cppper with negative $V_{r}$

Negative Shunt Cppper

Negative Shunt Cppper with positive $V_{r}$

Negative Shunt Cppper with negative $V_{r}$

Let us discuss each of these types in detail.

Negative Series Cppper

A Cppper circuit in which the diode is connected in series to the input signal and that attenuates the negative portions of the waveform, is termed as Negative Series Cppper. The following figure represents the circuit diagram for negative series cppper.

Positive Cycle of the Input − When the input voltage is appped, the positive cycle of the input makes the point A in the circuit positive with respect to the point B. This makes the diode forward biased and hence it acts pke a closed switch. Thus the input voltage completely appears across the load resistor to produce the output $V_{0}$.

Negative Cycle of the Input − The negative cycle of the input makes the point A in the circuit negative with respect to the point B. This makes the diode reverse biased and hence it acts pke an open switch. Thus the voltage across the load resistor will be zero making $V_{0}$ zero.

Waveforms

In the above figures, if the waveforms are observed, we can understand that only a portion of the negative peak was cppped. This is because of the voltage across $V_{0}$. But the ideal output was not meant to be so. Let us have a look at the following figures.

Unpke the ideal output, a bit portion of the negative cycle is present in the practical output due to the diode conduction voltage which is 0.7v. Hence there will be a difference in the practical and ideal output waveforms.

Negative Series Cppper with positive $V_{r}$

A Cppper circuit in which the diode is connected in series to the input signal and biased with positive reference voltage $V_{r}$ and that attenuates the negative portions of the waveform, is termed as Negative Series Cppper with positive $V_{r}$. The following figure represents the circuit diagram for negative series cppper when the reference voltage appped is positive.

During the positive cycle of the input, the diode starts conducting only when the anode voltage value exceeds the cathode voltage value of the diode. As the cathode voltage equals the reference voltage appped, the output will be as shown.

Negative Series Cppper with negative $V_{r}$

A Cppper circuit in which the diode is connected in series to the input signal and biased with negative reference voltage $V_{r}$ and that attenuates the negative portions of the waveform, is termed as Negative Series Cppper with negative $V_{r}$. The following figure represents the circuit diagram for negative series cppper, when the reference voltage appped is negative.

During the positive cycle of the input the diode gets forward biased and the input signal appears at the output. During its negative cycle, the diode gets reverse biased and hence will not conduct. But the negative reference voltage being appped, appears at the output. Hence the negative cycle of the output waveform gets cppped after this reference level.

Negative Shunt Cppper

A Cppper circuit in which the diode is connected in shunt to the input signal and that attenuates the negative portions of the waveform, is termed as Negative Shunt Cppper. The following figure represents the circuit diagram for negative shunt cppper.

Positive Cycle of the Input − When the input voltage is appped, the positive cycle of the input makes the point A in the circuit positive with respect to the point B. This makes the diode reverse biased and hence it behaves pke an open switch. Thus the voltage across the load resistor equals the appped input voltage as it completely appears at the output $V_{0}$

Negative Cycle of the Input − The negative cycle of the input makes the point A in the circuit negative with respect to the point B. This makes the diode forward biased and hence it conducts pke a closed switch. Thus the voltage across the load resistor becomes zero as no current flows through it.

Waveforms

In the above figures, if the waveforms are observed, we can understand that just a portion of the negative peak was cppped. This is because of the voltage across $V_{0}$. But the ideal output was not meant to be so. Let us have a look at the following figures.

Unpke the ideal output, a bit portion of the negative cycle is present in the practical output due to the diode conduction voltage which is 0.7v. Hence there will be a difference in the practical and ideal output waveforms.

Negative Shunt Cppper with positive $V_{r}$

A Cppper circuit in which the diode is connected in shunt to the input signal and biased with positive reference voltage $V_{r}$ and that attenuates the negative portions of the waveform, is termed as Negative Shunt Cppper with positive $V_{r}$. The following figure represents the circuit diagram for negative shunt cppper when the reference voltage appped is positive.

During the positive cycle of the input the diode gets reverse biased and behaves as an open switch. So whole of the input voltage, which is greater than the reference voltage appped, appears at the output. The signal below reference voltage level gets cppped off.

During the negative half cycle, as the diode gets forward biased and the loop gets completed, no output is present.

Negative Shunt Cppper with negative $V_{r}$

A Cppper circuit in which the diode is connected in shunt to the input signal and biased with negative reference voltage $V_{r}$ and that attenuates the negative portions of the waveform, is termed as Negative Shunt Cppper with negative $V_{r}$. The following figure represents the circuit diagram for negative shunt cppper, when the reference voltage appped is negative.

During the positive cycle of the input the diode gets reverse biased and behaves as an open switch. So whole of the input voltage, appears at the output $V_{o}$. During the negative half cycle, the diode gets forward biased. The negative voltage up to the reference voltage, gets at the output and the remaining signal gets cppped off.

Two-way Cppper

This is a positive and negative cppper with a reference voltage $V_{r}$. The input voltage is cppped two-way both positive and negative portions of the input waveform with two reference voltages. For this, two diodes $D_{1}$ and $D_{2}$ along with two reference voltages $V_{r1}$ and $V_{r2}$ are connected in the circuit.

This circuit is also called as a Combinational Cppper circuit. The figure below shows the circuit arrangement for a two-way or a combinational cppper circuit along with its output waveform.

During the positive half of the input signal, the diode $D_{1}$ conducts making the reference voltage $V_{r1}$ appear at the output. During the negative half of the input signal, the diode $D_{2}$ conducts making the reference voltage $V_{r1}$ appear at the output. Hence both the diodes conduct alternatively to cpp the output during both the cycles. The output is taken across the load resistor.

With this, we are done with the major cppper circuits. Let us go for the clamper circuits in the next chapter.