Material and application of varactor diode
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Material and application of varactor diode
Most of the materials are single crystal silicon or gallium arsenide, and the epitaxial technology is adopted. The larger the reverse bias voltage is, the smaller the junction capacitance is. The varactor diode has a series resistance related to the resistivity of the substrate material. For different purposes, varactor diodes with different C and VR characteristics shall be selected, such as those for resonance circuit tuning, for reference, and for frequency doubling and phase shifting in solid power sources.
purpose
Small power diodes for AFC and tuning are called varactor diodes. The electrostatic capacity of PN junction is changed by applying reverse voltage. Therefore, it is used for automatic frequency control, scanning oscillation, frequency modulation and tuning. Generally, although silicon diffused diodes are used, special diodes can also be made of alloy diffused, epitaxial combined, double diffused and so on, because the change rate of electrostatic capacity of these diodes is very large for voltage. The junction capacitance changes with the reverse voltage VR, instead of the variable capacitance, and is used as the tuning circuit, oscillation circuit, and phase-locked loop. It is commonly used in the channel conversion and tuning circuit of the TV high frequency head, mostly made of silicon material. By changing the resonant frequency of the varactor diode, the whole range of the required capacitance in the parallel resonant band-pass filter can be obtained. (for tuning circuit).