1. Rectification: Rectifier diodes are mainly used in rectifier circuits, converting alternating current (AC) into pulsating direct current (DC). Rectifier diodes are all junction diodes (JDs), resulting in large junction capacitance and consequently, relatively low operating frequencies, typically below 3kHz.
2. Switching: Under forward bias, a diode has very low resistance and is in a conducting state, acting like a closed switch. Under reverse bias, its resistance is very high and it is in a cutoff state, acting like an open switch. These switching characteristics can be used to construct various logic circuits.
3. Limiting: When a diode is forward biased, its forward voltage drop remains essentially constant (0.7V for silicon diodes, 0.3V for germanium diodes). This characteristic allows it to be used as a limiting element in circuits to restrict signal amplitude within a certain range.
4. Freewheeling: Diodes act as freewheeling elements in the inductors of switching power supplies and in inductive loads such as relays.
5. Detection: The main function of detector diodes is to detect low-frequency signals within high-frequency signals. They are point-contact type diodes. Its junction capacitance is small, and its operating frequency is relatively high. It is generally made of germanium.
6. Damping: Damping diodes are mostly used in high-frequency voltage circuits. They can withstand high reverse breakdown voltage and large peak current. They are commonly used in television circuits. Commonly used damping diodes include 2CN1, 2CN2, and BSBS44.
7. Display: Used in VCD, DVD, calculator, and other displays.
8. Zener: This type of diode utilizes the reverse breakdown characteristic of a diode. In a circuit, the voltage across its terminals remains essentially constant, thus stabilizing the voltage. Commonly used Zener diodes include 2CW55 and 2CW56.
9. Trigger: Trigger diodes, also known as bidirectional trigger diodes (DIAC), are three-layer structures with symmetrical two-terminal semiconductor devices. They are often used to trigger bidirectional thyristors; and for overvoltage protection in circuits.
