In varactor diodes, the junction capacitance is controlled by ______ supply in _________ mode.

In varactor diodes, the junction capacitance is controlled by external supply in reverse biased mode.

Additional Information

Varactor diode:

• It is represented by a symbol of diode terminated in the variable capacitor as shown below:

• Varactor diode refers to the variable Capacitor diode, which means the capacitance of the diode varies linearly with the applied voltage when it is reversed biased.
• The junction capacitance across a reverse bias PN junction is given by

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• As the reverse bias voltage increases, the depletion region width increases resulting in a decrease in the junction capacitance.

•  Varactor diodes are used in electronic tuning systems to eliminate the need for moving parts
• Varactor [also called varicap, variable reactance diode, or tuning diode] diodes are the semiconductor, voltage-dependent, variable capacitors
• Varactors are used as voltage-controlled capacitors and it operated in a reverse-biased state. 
   

A varactor diode finds its applications in:

• Frequency converter
• Low noise parametric amplifier
• Harmonic frequency generator
• Varactor diodes can be used as frequency modulators
• In microwave receiver LO, varactor diodes can be used as frequency multipliers
• Varactor diodes can be used as RF phase shifters