electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...

, 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 components. A clipping circuit consists of linear elements like

resistor A resistor is a passive two-terminal electronic 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 e ...

s and non-linear elements like

diode A diode is a two-Terminal (electronics), terminal electronic component that conducts electric current primarily in One-way traffic, one direction (asymmetric electrical conductance, conductance). It has low (ideally zero) Electrical resistance ...

s or

transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

s, but it does not contain energy-storage elements like

capacitors In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...

. 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 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 connected between the voltage rails. This can be improved by replacing the lower resistor with a zener diode with a breakdown voltage 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. It may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism or electronic components. Depending on the ...

stabilising the reference voltage against supply and load variations.

Zener diode

In the example circuit on the right, two zener diodes 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 I-V curve 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 direct coupling, DC-coupled Electronic component, electronic voltage amplifier with a differential input, a (usually) Single-ended signaling, single-ended output, and an extremely high gain ( ...

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 In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...

. 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