The varactor diode is a special diode specially designed according to the principle that the junction capacitance of the “PN junction” inside the ordinary diode can change with the change of the applied reverse voltage.
The varactor diode is mainly used in the high-frequency modulation circuit of the mobile phone or landline in the cordless telephone to realize the modulation of the low-frequency signal to the high-frequency signal and emit it. In the working state, the varactor diode modulation voltage is generally added to the negative electrode Make the internal capacitance of the varactor diode change with the modulation voltage.
The varactor diode fails, mainly manifested as leakage or poor performance:
(1) When leakage occurs, the high-frequency modulation circuit will not work or the modulation performance will deteriorate.
(2) When the varactor performance is deteriorated, the operation of the high-frequency modulation circuit is unstable, and the modulated high-frequency signal is sent to the other party and received distortion by the other party.
When one of the above situations occurs, the varactor diode of the same model should be replaced.