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Is a diode an example of a variable capacitor?
Varactor or varicap circuit symbol The varactor diode or varicap diode is shown in circuit diagrams or schematics using a symbol that combines the diode and capacitor symbols. In this way it is obvious that it is being used as a variable capacitor rather than a rectifier.
Which diode is used as a variable capacitor?
varactor diode
In electronics, a varicap diode, varactor diode, variable capacitance diode, variable reactance diode or tuning diode is a type of diode designed to exploit the voltage-dependent capacitance of a reverse-biased p–n junction.
How does a variable capacitance diode work?
The Varactor diode is made up of n-type and p-type semiconductor material. The varactor diode operates only in reverse bias. Because of reverse bias, the current does not flow. If the diode is connected in forward biasing the current starts flowing through the diode and their depletion region become decreases.
What are variable capacitors called?
Variable capacitors are often used in L/C circuits to set the resonance frequency, e.g. to tune a radio (therefore it is sometimes called a tuning capacitor or tuning condenser), or as a variable reactance, e.g. for impedance matching in antenna tuners.
What is difference between a variable and fix capacitors?
There are two major types of capacitors: fixed and variable. Fixed capacitors have set capacitances because the parallel sheets of metal are at a fixed distance apart, while variable capacitors have the ability to change based on manipulation of the parallel plates.
What are variable air capacitors?
Variable air capacitors are used in circumstances where the capacitance needs to be varied. They are sometimes used in resonant circuits, such as radio tuners, frequency mixers or antenna impedance matching applications. Another use for variable capacitors is while prototyping an electronic circuit design.
What kind of diodes are variable capacitance diodes?
Diodes whose junction capacitance is variable with voltage are beginning to replace large bulky tuning capacitors. Here are the operating principles and important parameters. Varactor diodes, or variable-capacitance diodes, are semiconductor diodes that have been optimized for the capacitance effect under reverse-bias conditions.
How is a varicap diode used in a tuning circuit?
The varicap diode is normally used in a tuning circuit in these mentioned applications, as it functions as a variable capacitor in the circuit. Here is an example, this is a parallel resonant band-pass filter circuit where a varicap diode is used to adjust the resonant frequency over a specified range.
Why does a varactor have a high capacitance?
The capacitance effect in a varactor arises from the depletion region separating the p and n material in a diode. Recalling simple junction physics, the depletion region has a high resistivity because of the lack of mobile carriers and, as such, makes a good dielectric.
What happens when a reverse bias is applied to a diode?
When a reverse bias is applied to the diode, its junction capacitance varies. This characteristic of diode has been taken advantage by engineers to design a special-purpose diode called the Varicap diode.