How do you bias a varactor diode?
A varactor diode is a diodes is reverse bias capacitance can be varied by changing the reverese bias voltage. A diode is simply a PN junction. When reversed biased a positive voltage is applied to cathode and negative voltage is applied to the anode.
What is varactor diode and where it is used?
Varactor or varicap diodes are used mainly in radio frequency or RF circuits to provide voltage controlled variable capacitance. These electronic componenta can be used in a whole variety of ways where a capacitance level needs to be controlled by a voltage.
How does varactor diode work?
Definition: Varactor diode is the one which works on the principle of variation in capacitance by changing the width of the depletion region of P-N junction. The P-N Junction diode creates capacitor effect. The capacitance is controlled by applied voltage. It works on reverse biased mode.
Who invented varactor diode?
Erik Kollberg
The device was invented by Erik Kollberg together with Anders Rydberg in 1989 at Chalmers University of Technology.
How does varactor modulator work?
Varactor diode modulator is the direct method of FM generation wherein the carrier frequency is directly varied by the modulating signal. A varactor diode is a semiconductor diode whose junction capacitance varies linearly with applied voltage when the diode is reverse biased. for generation of FM wave.
Under what bias condition is a varactor operated?
Varactor diodes are normally operated in the reverse bias condition. When the reverse bias increases, the width of the depletion region also increases resulting in less capacitance. This means when reverse bias decreases, a corresponding increase in capacitance can be seen.
What does a varactor do?
A varactor diode is a simple variable capacitor that allows oscillator circuits and other circuits to be easily tuned by applying a voltage. These diodes have a similar structure as a p-n diode; the structure of a varactor diode is rather simple and illustrates its power as a component with nonlinear reactance.
What is varactor diode modulator?
What is varactor modulator?
Varactor diode modulator is the direct method of FM generation wherein the carrier frequency is directly varied by the modulating signal. Varactor diodes are used along with reactance modulator to provide automatic frequency correction for an FM transmitter. The varactor diode modulator circuit is shown in Fig5.
How does photodiode and varactor work?
A varactor diode is designed to store electric charge not to conduct electric current. So varactor diode should always be operated in reverse bias. When a reverse bias voltage is applied, the electrons from n-region and holes from p-region moves away from the junction.
How is reverse bias applied to a varactor diode?
The varactor diode requires the reverse bias to be applied across the diode in a way that does not affect the operation of the tuned circuit of which it is part. Care must be taken to isolate the bias voltage from the tuning circuit so that the RF performance is not impaired.
How is the varactor diode similar to a capacitor?
The term varactor is originated from a variable capacitor. Varactor diode operates only in reverse bias. The varactor diode acts like a variable capacitor under reverse bias. Varactor diode is also sometimes referred to as varicap diode, tuning diode, variable reactance diode, or variable capacitance diode.
How is junction capacitance related to reverse bias voltage?
The junction capacitance is inversely proportional to the width of depletion layer i.e. if the width of depletion layer is less, the capacitance will be more, and vice versa. So if we need to increase the capacitance of a varactor diode, the reverse bias voltage should be decreased.
Which is the varactor in the parallel resonance circuit?
The varactor diode is small in size and less in weight. The figure below shows that D 1 and D 2 are the two Varactor diode. These diodes provide the variable resistance in the parallel resonance circuit. The V c is the DC voltage used for controlling the reverse voltage of the diode.