VARACTOR DIODE

Varactor Diode

• A varactor diode is a type of diode whose internal capacitance changes when the voltage is turned around.
• It always works with reverse bias and is a semiconductor device that depends on voltage.
• Varicap, Voltcap, Voltage changeable capacitance, and Tunning diode are some of the names for the varactor diode.

Symbol of Varactor Diode

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• The following picture makes it clear that the varactor diode's symbol looks a lot like the PN-junction diode's.
• The anode and cathode are the two ends of the diode.
• The diode is at one end of the sign, and the capacitor's conducting plates are shown by two parallel lines at the other. The dielectric is shown by the space between the plates.

Operation of Varactor Diode

• The varactor diode's job is to store charges, so it is always used in reverse bias situations.
• Electricity moves when a forward bias voltage is put on it. This makes the decline area almost invisible, which is not what we want.
• A p-n junction diode's junction capacitance goes down as the width of the depletion layer gets bigger. That is, the capacitance goes up when the width of the depletion layer goes down and down. This means that the reverse bias voltage should be lowered if we want to make the capacitance of a varactor diode bigger.
• The thickness of the depletion layer gets smaller, which makes the capacitance go up. In the same way, raising the reverse bias voltage should make the capacitance go down.
• The best thing about a varactor diode over a regular changeable capacitor is that it lets you get different capacitance values by just changing the voltage.

Varactor Diode Applications

     The following points show some ways that varactor diodes can be used.

• People work with them in RF design, and they let you change the capacitance in a circuit by adding a control voltage. Because it gives them unique properties, varactor diodes are used in the RF business.
• There are a lot of systems that use these diodes, but they are mostly used in two areas.
• FR filters—Variable diodes can be used to tune filters. In front-end receiver circuits, tracking filters may be needed so that the filters can keep track of the frequency of inbound signals.
• Voltage-controlled oscillators (VCOs): VCOs are useful in many situations, but they work best in oscillators that are part of a phase-locked loop. It is possible to find VCOs in almost all radios and wireless devices.

IMAGE SOURCE (THUMBNAIL)