Clipper and clamper circuits

Clipper and clamper circuits

1. Clipper And Clamper Circuits By Unsa Shakir

2. What are clipper circuits? Clippers Circuits are used to remove the part of a signal that is above or below some defined reference level. One of the simple example of a clipper is the half-wave rectifier – that circuit basically cut off everything at the reference level of zero and let only the positive-going or negative-going portion of the input waveform. Clipping circuits (also known as limiters, amplitude selector or slicers) Depending on the orientation of the diode, the positive or negative region of the input signal is “clipped” off.

3. Types of Clippers Circuits Unbiased Clipper Circuit U nb i ased Positive clipper U nb i ased Nega t iv e clipper Biased clipper circuit Biased po s i t i v e clipper Biased negat i v e clipper Clipper series circuits

4. Unbiased positive Clippers  Positive clippers are used to clip positive portions of the input signal and allow the negative portions of the signal to pass through Figure below shows the input and output signal along with the positive clipper. The positive cycle is completely clipped off by the clipper . During the positive half cycle of the input waveform, the diode ‘D’ is reverse biased, which maintains the output voltage at 0 Volts. This causes the positive half cycle to be clipped off. Dur­ing the negative half cycle of the input, the diode is forward biased and so the nega­tive half cycle appears across the output.

5. Unbiased Negative clippers  Negative clippers are used to clip Negative portions of the input signal and allow the positive portions of the signal to pass through  Figure shows the input and output signal along with the negative clipper. The negative cycle is completely clipped off by the clipper. The diode in forward biased configuration can be modelled as an close switch. This is indicated in the figure. As the diode acts as closed switch , current flows through the load and hence output appears across the load. This is the reason why the negative cycle is completely clipped off.

6. Biased positive clipper  As shown earlier, we saw that the clipping of the signal takes place as soon as the input signal goes positive. If we want to change/adjust the clipping level of AC voltage, then external biasing voltage must be used. The figure given below shows a biased (series) clipper.

7. Working: A biased clipper comes in handy when a small portion of positive or negative half cycles of the signal voltage is to be removed. When a small portion of the positive half cycle is to be removed, it is called a biased positive clipper. It is similar to the series positive clipper in addition to a negative reference voltage in series with a resistor; and here, during the positive half cycle, the output appears across the resistor as a negative reference voltage. During the negative half cycle, the output is generated after reaching a value greater than the negative reference voltage Instead of negative reference voltage a positive reference voltage is connected to obtain series positive clipper with a positive reference voltage. During the positive half cycle, the reference voltage appears as an output across the resistor, and during the negative half cycle, the entire input appears as output across the resistor.

8. Biased negative Clipper  As shown earlier, we saw that the clipping of the signal takes place as soon as the input signal goes negative. If we want to change/adjust the clipping level of AC voltage, then external biasing voltage must be used. The figure given below shows a biased (series) clipper.

9. Working: A biased clipper comes in handy when a small portion of positive or negative half cycles of the signal voltage is to be removed. When a small portion of the negative half cycle is to be removed, it is called a biased negative clipper. Series negative clipper with positive reference voltage is similar to the series negative clipper, but in this a positive reference voltage is added in series with the resistor. During the positive half cycle, the diode start conducting only after its anode voltage value exceeds the cathode voltage value. The series negative clipper with a negative reference voltage is similar to the series negative clipper with positive reference voltage, but instead of positive Vr here a negative Vr is connected in series with the resistor, which makes the cathode voltage of the diode as negative voltage. Thus during the positive half cycle, the entire input appears as output across the resistor, and during the negative half cycle, the input appears as output until the input value will be less than the negative reference voltage

10. Clamper circuit A clamper is an electronic circuit that changes the DC level of a signal to the desired level without changing the shape of the applied signal. In other words, the clamper circuit moves the whole signal up or down to set either the positive peak or negative peak of the signal at the desired level. A clamper circuit is also called as a  Level Shifter . Clamper circuits consist of energy storage elements like capacitors. A simple clamper circuit comprises of a capacitor, a diode, a resistor and a dc battery if required.

11. Types Of Clamper Circuits The direction of the diode in the clamping circuit determines the clamper circuit type. The operation of a clamping circuit is mainly based on the switching time constants of the capacitor. However, capacitor in the circuit charges through the diode and discharges through the load . Negative clamper Positive clamper

12. Negative Clamper The Negative Clamping circuit consists of a diode connected in parallel with the load. The capacitor used in the clamping circuit can be chosen such that it must charge very quickly and it should not discharge very drastically. The anode of the diode is connected to the capacitor and cathode to the ground . This type of clamping circuit shifts the input waveform in a negative direction, as a result the waveform lies below a DC reference voltage

13. During the positive half cycle of the input, the diode is in forward bias and as the diode conducts the capacitor charges very quickly. During the negative half cycle of the input, the diode will be in reverse bias and the diode will not conduct, the output voltage will be equal to the sum of the applied input voltage and the charge stored in the capacitor during reverse bias. The output waveform is same as input waveform, but shifted below 0 volts.

14. Positive Clamper The circuit of the positive clamper is similar to the negative clamper but the direction of the diode is inverted in such a way that the cathode of the diode is connected to the capacitor . This type of clamping circuit shifts the input waveform in a positive direction, as a result the waveform lies above a DC reference voltage. A Clamping circuit restores the DC level. When a negative peak of the signal is raised above to the zero level, then the signal is said to be positively clamped.

15. During the positive half wave cycle, output voltage of the circuit will be the sum of applied input voltage and the charge stored at capacitor. During the negative half wave cycle, the diode starts to conduct and charges the capacitor very quickly to its maximum value. The output waveform of the positive clamper shifts towards the positive direction above the 0 volts