Diodes - Variable Capacitance (Varicaps, Varactors)

Variable capacitance diodes, also known as varicaps or varactors, are a type of diode that is used to vary the capacitance of a circuit. A varicap diode consists of a p-n junction that is reverse-biased, which causes the depletion region to expand and contract in response to changes in the applied voltage. This change in the size of the depletion region alters the capacitance of the diode, allowing it to be used as a variable capacitor in a circuit. Varicap diodes are commonly used in applications such as frequency control and tuning, where they are used to vary the capacitance of a circuit in order to change its resonant frequency. They are also used in phase-locked loop (PLL) circuits, where they are used to control the phase of a signal.