The varactor diode is a special diode specially designed based on the principle that the junction capacitance of the internal "PN junction" of the ordinary diode can change with the change of the applied reverse voltage.
Varactor diodes are mainly used in the high-frequency modulation circuit of mobile phones or landlines in cordless telephones to achieve modulation of low-frequency signals to high-frequency signals and transmit them.
In the working state, the modulation voltage of the varactor diode is generally added to the negative electrode, so that the internal junction capacitance of the varactor diode changes with the change of the modulation voltage.
