What is a varactor diode, its structure, principle, type, application, and manufacturing process 1

Varactor diode is a type of capacitor diode, which is unique in that its capacitance changes with the reverse bias voltage. It is a device widely used in the field of radio electronics, which can be used in circuits such as frequency modulation, frequency synthesis, frequency conversion, ATMEGA64-16AU oscillator, filters, etc. This article will provide a detailed introduction to the structure, working principle, performance characteristics, and applications of varactor diodes.

1、 Basic structure

Varactor diode, also known as capacitive modulation diode, is a diode with variable capacitance. Its structure is similar to a normal diode, consisting of P-type and N-type semiconductors, but there is a highly doped region between its P-type and N-type regions, also known as the modulation region or varactor region. The width of the modulation region determines the capacitance of the diode, hence it is called a varactor diode.

2、 Principle

A varactor diode, like a regular diode, has one end connected to a P-type semiconductor and the other end connected to an N-type semiconductor. When forward biased, an external electric field pushes the carriers between the P-type and N-type regions towards the PN junction, narrowing it and reducing its capacitance; When reverse biased, the carriers between the P-type region and the N-type region are pulled apart by the electric field, causing the PN junction to widen and the capacitance to increase. Therefore, the capacitance of a varactor diode can be adjusted by controlling its bias voltage. When the bias voltage of the varactor diode is different, its capacitance value is also different, so it can be used to make variable capacitors.diode