CLIPPERS AND CLAMPERS IN ELECTRONICS PDF

A clipper which removes a portion of positive half cycle of the input signal is called positive clipper. A clipper circuit that removes the negative half cycle is called negative clipper. It consists of a diode D and a resistor R with outputs taken across the resistor. During positive half cycle of the input voltage, the terminal A is positive with respect to B.

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Applications of Clampers Introduction Most of the electronic circuits like amplifiers, modulators and many others have a particular range of voltages at which they have to accept the input signals.

Any of the signals that have an amplitude greater than this particular range may cause distortions in the output of the electronic circuits and may even lead to damage of the circuit components.

In view of the fact that most of the electronic devices work on a single positive supply, the input voltage range would also be on the positive side. Since the natural signals like audio signals, sinusoidal waveforms and many others contain both positive and negative cycles with varying amplitude in their duration. These waveforms and other signals have to be modified in such a way that the single supply electronic circuits can be able to operate on them.

The clipping of a waveform is the most common technique that applies to the input signals to adapt them so that they may lie within the operating range of the electronic circuits. The clipping of waveforms can be done by eliminating the portions of the waveform which crosses the input range of the circuit.

Clippers can be broadly classified into two basic types of circuits. They are: series clippers and shunt or parallel clippers.

Series clipper circuit contains a power diode in series with the load connected at the end of the circuit. The shunt clipper contains a diode in parallel with the resistive load. The half — wave rectifier circuit is similar to a series clipper circuit. If the diode in series clipper circuit is in forward bias condition, the output waveform at the load follows the input waveform.

When the diode is in reverse bias and it is unable to conduct current, the output of the circuit is nearly zero volts.

The direction of the connected diode determines the polarity of the clipped output waveform. If the diode symbol points toward the source and is connected to the positive terminal of the supply, the circuit will be a positive series clipper, resembles that it clips off the positive alternation or cycle of the input sinusoidal waveform. If the diode symbol points toward the connected load, then the circuit will be a negative series clipper, resembles that it clips off the negative alternation or cycle of the input sinusoidal waveform.

In contrast to the series clipper circuit, a shunt clipper circuit provides the output when the diode is connected in reverse bias and when it is not conducting. When the diode is non — conducting, the shunt combination diode acts as an open circuit and both the series resistor and load resistor acts as a voltage divider.

The series limiting resistor is connected in series with the supply to prevent the diode from short circuits. It depends on the polarity of the shunt clipper which is determined by the direction of diode connection. Above biased clipper circuit is a shunt clipper circuit which uses the DC supply voltage to bias the diode. It is the biasing voltage at which the diode starts conducting. The diode in the shunt clipper circuit starts to conduct when it reaches the biasing voltage. Clipper circuits are used in a variety of systems to perform one of the two functions: Altering the waveform shapes Protecting the circuits from transients The first application is commonly noticed in the operation of half-wave rectifiers that changes the varying voltage into an output pulsating DC waveform.

A transient is defined as an abrupt change in current or voltage with extremely short duration. Clipper circuits can be used to protect the sensitive circuits from transient effects. Types of Clipper Circuits Cathode is connected to the power supply and anode is maintained at ground potential. Series Negative Clipper Anode is connected to the power supply and the cathode is maintained at ground potential. Shunt Positive Clipper Anode is connected to the the power supply through a resistor R and the cathode is at ground potential.

Shunt Negative Clipper Cathode is connected to the power supply through a resistor R and anode is maintained at ground potential. Series Positive Clipper with Positive Bias Voltage Positive Half Cycle: Cathode is connected to the positive supply and the anode is maintained at positive bias potential.

The diode is reverse biased during the whole positive half cycle. Series Positive Clipper with Negative Bias Voltage Positive Half Cycle: Cathode is connected to the positive supply and the anode is maintained at negative bias potential. The diode is forward biased during the whole positive half cycle. The diode will be forward biased during the negative cycle. Series Negative Clipper with Positive Bias Voltage Positive Half Cycle: In this case the anode is connected to the positive supply and the cathode is maintained at positive bias potential.

Series Negative Clipper with Negative Bias Voltage Connected in Parallel Positive Half Cycle: In this circuit the anode is connected to the positive supply and the cathode is maintained at negative bias potential. The diode will be reverse biased during the negative cycle. Shunt Positive Clipper with Positive Shunt Bias Voltage Positive Half Cycle: In this circuit, anode is connected to the positive supply and the cathode is maintained at positive bias potential. Shunt Positive Clipper with Negative Shunt Bias Voltage Positive Half Cycle: In this circuit, anode node is connected to the positive supply and the cathode is maintained at negative bias potential.

Shunt Negative Clipper with Positive Bias Voltage Positive Half Cycle: Cathode is connected to the positive supply and the anode is maintained at positive bias potential. Similarly anode of diode D2 is maintained at -Vdc2 and its cathode observes a variable positive voltage. The diode D2 will be completely reverse biased during the whole positive half cycle. Similarly anode of diode D2 is maintained at -Vdc2 and its cathode observes a variable negative voltage. The diode D1 will be completely reverse biased during the whole negative half cycle.

This type of circuit is called as Parallel based Clipper. It uses two diodes and two voltage sources connected in opposite directions. Diode Clampers Clampers can also be referred as DC restorers.

Clamping circuits are designed to shift the input waveform either above or below the DC reference level without altering the waveform shape. This shifting of the waveform results in a change in the DC average voltage of the input waveform. The levels of peaks in the signal can be shifted using the clamper circuit, hence clampers can also be referred as level shifters.

Clampers can be broadly classified into two types. They are positive clampers and negative clampers. Positive Clamper: This type of clamping circuit shifts the input waveform in a positive direction, as a result the waveform lies above a DC reference voltage.

Negative Clamper: This type of clamping circuit shifts the input waveform in a negative direction, as a result the waveform lies below a DC reference voltage. 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.

Types of Clamper Circuits 1. 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. 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.

Negative Clamper with Positive Reference Voltage The circuit arrangement is very similar to the Negative clamper circuit, but a DC reference supply is connected in series with the diode. The output waveform is also similar to the Negative clamper output waveform, but it is shifted towards the positive direction by an amount equal to the reference voltage at the diode.

Negative Clamper with Negative Reference Voltage If the reference voltage directions in the above case are reversed and connected to the diode in series, then during the positive half cycle the diode starts conducting current before applying input voltage.

Since the cathode has a very small negative reference voltage less than zero volts, the waveform is shifted away from the 0 volts towards the negative direction by an amount of the reference voltage. 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.

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.

Positive Clamper with Positive Reference Voltage A positive reference voltage is connected in series with the diode in the positive clamper circuit such that the positive terminal of the reference voltage is connected in series with the anode of the diode. If once the cathode voltage is greater than anode voltage, the diode stops conduction of electric current. During the negative half cycle, the diode conducts and charges the capacitor very quickly.

Positive Clamper with Negative Reference Voltage The direction of the reference voltage is reversed in this case such that the negative terminal of the reference voltage is connected in series with the anode of diode reflecting it as a negative reference voltage. During the positive half wave cycle of the input waveform, the diode does not conduct, as a result the output is equal to voltage stored in the capacitor and applied input voltage.

During the negative half cycle, the diode starts conducting current solely after the cathode voltage value is less than the anode voltage. Clippers can be used as freewheeling diodes in protecting the transistors from transient effects by connecting the diodes in parallel with the inductive load. Commonly used in power supplies. In the separation of synchronizing signals existing from the composite color picture signals. Frequently used in FM transmitters for removing the excess ripples in the signals above a certain noise level.

Applications of Clampers Clampers can be frequently used in removing the distortions and identification of polarity of the circuits.

For improving the reverse recovery time, clampers are used. Clamping circuits can be used as voltage doublers and for modelling the existing waveforms to a required shape and range. Clampers are widely used in test equipments and other sonar systems.

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Positive unbiased[ edit ] A positive unbiased clamp. In the negative cycle of the input AC signal, the diode is forward biased and conducts, charging the capacitor to the peak negative value of VIN. During the positive cycle, the diode is reverse biased and thus does not conduct. This is also called a Villard circuit. Negative unbiased[ edit ] A negative unbiased clamp A negative unbiased clamp is the opposite of the equivalent positive clamp. In the positive cycle of the input AC signal, the diode is forward biased and conducts, charging the capacitor to the peak positive value of VIN.

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