What is a crystal diode?

The crystal diode is usually represented by a "D" plus a number in the circuit, such as: D5 represents a diode numbered 5.

Function: The main characteristic of the diode is unidirectional conductivity, that is, the on-resistance is small under the action of the forward voltage; and the on-resistance is extremely large or infinite under the action of the reverse voltage.

Because the diode has the above characteristics, it is often used in cordless telephones in circuits such as rectification, isolation, voltage regulation, polarity protection, code control, frequency modulation and squelch. The crystal diodes used in telephones can be divided into: Rectifier diodes (such as 1N4004), isolation diodes (such as 1N4148), Schottky diodes (such as BAT85), LEDs, Zener diodes, etc.