electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, a clipper is a circuit designed to prevent a signal from exceeding a predetermined reference voltage level. A clipper does not distort the remaining part of the applied waveform. Clipping circuits are used to select, for purposes of transmission, that part of a signal waveform which lies above or below the predetermined reference voltage level. Clipping may be achieved either at one level or two levels. A clipper circuit can remove certain portions of an arbitrary waveform near the positive or negative peaks or both. Clipping changes the shape of the waveform and alters its

spectral component In telecommunications, spectral component is any of the waves that range outside the interval of frequencies assigned to a signal. Any waveform can be disassembled into its spectral components by Fourier analysis or Fourier transformation. The ...

s. A clipping circuit consists of linear elements like

resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

s and non-linear elements like

diode A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode ...

s or

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

s, but it does not contain energy-storage elements like capacitors. Clipping circuits are also called ''slicers'' or ''amplitude selectors''.

Types

Diode clipper

A simple diode clipper can be made with a diode and a resistor. This will remove either the positive, or the negative half of the waveform depending on the direction the diode is connected. The simple circuit clips at zero voltage (or to be more precise, at the small

forward voltage Forward is a relative direction, the opposite of backward. Forward may also refer to: People *Forward (surname) Sports * Forward (association football) * Forward (basketball), including: ** Point forward ** Power forward (basketball) ** Smal ...

of the forward biased diode) but the clipping voltage can be set to any desired value with the addition of a reference voltage. The diagram illustrates a positive reference voltage but the reference can be positive or negative for both positive and negative clipping giving four possible configurations in all. The simplest circuit for the voltage reference is a resistor

potential divider In electronics, a voltage divider (also known as a potential divider) is a passive linear circuit that produces an output voltage (''V''out) that is a fraction of its input voltage (''V''in). Voltage division is the result of distributing the inp ...

connected between the voltage rails. This can be improved by replacing the lower resistor with a

zener diode A Zener diode is a special type of diode designed to reliably allow current to flow "backwards" (inverted polarity) when a certain set reverse voltage, known as the ''Zener voltage'', is reached. Zener diodes are manufactured with a great varie ...

with a

breakdown voltage The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to experience electrical breakdown and become electrically conductive. For diodes, the breakdown voltage is the minimum reverse voltage that mak ...

equal to the required reference voltage. The zener acts as a

voltage regulator A voltage regulator is a system designed to automatically maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components ...

stabilising the reference voltage against supply and load variations.

Zener diode

In the example circuit on the right, two

s are used to clip the voltage V_IN. The voltage in either direction is limited to the reverse breakdown voltage ''plus'' the forward voltage drop across one zener diode.

Op-amp precision clipper

For very small values of clipping voltage on low-level signals the

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of the diode can result in clipping onset that is not very sharp. Precision clippers can be made by placing the clipping device in the feedback circuit of an

operational amplifier An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to c ...

in a manner similar to precision rectifiers.

Classification

Clippers may be classified into two types based on the positioning of the diode. * 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 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 element (potential source) in series with the diode. In the following diagrams the green plot is the input voltage, the orange plot is the output voltage, and the blue plot is the clipping level voltage.

Positively biased diode clipper

Negatively biased diode clipper

Combinational two-level diode clipper

The signal can be clipped to between two levels by using both types of diode clippers in combination. Rao K Venkata, ''Pulse And Digital Circuits'', Pearson, 2010, page 163,

Clamping circuit

A clamper circuit is not a clipper, but the simple diode version has a similar topology to a clipper with the exception that the resistor is replaced with a

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...

. The clamper circuit fixes either the positive or negative peaks at a fixed voltage (determined by the biasing voltage) rather than clipping them off.

References

External links

An overview of Clipping Circuits
Circuits Today {{DEFAULTSORT:Clipper (Electronics) Electronic circuits