For ease of understanding, it can be imagined as an electronic "check valve":
Forward direction (open): when the voltage is applied to the diode in the proper direction (the positive electrode is connected to the high potential and the negative electrode is connected to the low potential), the valve opens and the current can pass through smoothly.
Reverse (Close): When the voltage is applied to the diode in the opposite direction, the valve closes and the current cannot pass through (in fact, there is a very small leakage current, which is usually negligible).
Classification and application of diode
● Rectifier Diode: Converts alternating current (AC) to pulsating direct current (DC), common in power adaptors.
● Switching diode: refers to "1" and "0" in digital circuit by making use of its conduction and cut-off state, and also used in high-frequency circuit.
● Regulator diode (Zener diode): it works in the reverse breakdown zone and can keep the voltage at both ends basically unchanged when the current changes. It is used to provide stable reference voltage.
● Light emitting diode (LED): when conducting in the forward direction, the electron and hole are combined, and the excess energy is released in the form of light. Widely used in indicator lights, lighting and screens.
● Photodiode (PD): in contrast to LED, it generates weak current when illuminated, and is used for photosensitive sensor, remote control receiver, etc.
● Schottky diode: lower on-voltage (about 0.2-0.4V), extremely fast switching speed, commonly used in high frequency circuit and switching power supply.
