Clipper (electronics)

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In electronics, a clipper is a device designed to prevent the output of a circuit from exceeding a predetermined voltage level without distorting the remaining part of the applied waveform.

A clipping circuit consists of linear elements like resistors and non-linear elements like junction diodes or transistors, but it does not contain energy-storage elements like capacitors. Clipping circuits are used to select for purposes of transmission, that part of a signal wave form which lies above or below a certain reference voltage level.

Thus a clipper circuit can remove certain portions of an arbitrary waveform near the positive or negative peaks. Clipping may be achieved either at one level or two levels. Usually under the section of clipping, there is a change brought about in the wave shape of the signal.

Clipping circuits are also called slicers, amplitude selectors or limiters.

Types

Zener diode

Two shunt diode clipper circuits

In the example circuits above, one or two zener diodes are used to clip the voltage VIN. In the first circuit, the voltage is clipped to the reverse breakdown voltage of the zener diode. The output voltage in the first circuit should also never be more negative than the diode's forward voltage (such as .7V for a typical diode), but it is not shown in the picture. In the second, the voltage in either direction is limited to the reverse breakdown voltage plus the voltage drop across one zener diode.

Diodes

Examples of a waveform clipper from a circuit with diodes

Diodes can be applied to a circuit with other elements to reduce the susceptibility of the circuit to damage by overvoltage. It can also be used for creating special waveforms. In the image example, R1 is used to reduce the chance of flow of a high current through the diode, R2 induces a lower-level clipping at the output, and R3 induces an upper-level clipping at the output.

Classification

Clippers may be classified into two types based on the positioning of the diode. [1]

  • Series Clippers, where the diode is in series with the load resistance, and
  • Shunt Clippers, where the diode is shunted across the load resistance.

The diode capacitance affects the operation of the clipper at high frequency and influences the choice between the above two types. High frequency signals are attenuated in the shunt clipper as the diode capacitance provides an alternative path to output current. In the series clipper, clipping effectiveness is reduced for the same reason as the high frequency current passes through without being sufficiently blocked.

Clippers may be classified based on the orientation(s) of the diode. The orientation decides which half cycle is affected by the clipping action.

The clipping action can be made to happen at an arbitrary level by using a biasing elements (potential sources) in series with the diode.

  • Positively Biased Diode Clipper
  • Negatively Biased Diode Clipper

The signal can be clipped to between two levels by using both types of diode clippers in combination. [2] This clipper is referred to as

  • Combinational Diode Clipper or Two-Level Clippers

The clamping network is the one that will "clamp" a signal to a different dc level. The network must have capacitor, a diode, and a resistive element, but it also employs an independent dc supply to introduce an additional shift.

References

  1. ↑ Salivahanan, Electronic devices and circuits. 2nd Edition. Tata McGraw Hill, 2008, Page 555, ISBN 0-07-066049-2
  2. ↑ Rao K Venkata, Pulse And Digital Circuits, Pearson, 2010, page 163, ISBN 978-81-317-2135-3

See also

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