There are many different classifications of diodes, each of which has different functions and is different from each other. It is important to select appropriate products according to their different characteristics.

1. Rectifier diode

In principle, the DC output from the input AC is a rectifier. Taking the size of rectification current (100mA) as the boundary, the output current greater than 100mA is usually called rectification.

2. Limiting diode

After the diode is turned on in the forward direction, its forward voltage drop is basically unchanged (0.7V for silicon tube). Using this feature, as a limiting element in the circuit, the signal amplitude can be limited within a certain range. Most diodes can be used as limiting. There are also special limiting diodes for protecting instruments and high-frequency zeners. In order to make these diodes have a particularly strong role in limiting sharp amplitude, diodes made of silicon materials are usually used.

3. Switch diode

Under the action of forward voltage, the resistance is very small, and it is in the conduction state, which is equivalent to a switch on; Under the action of reverse voltage, the resistance is very large, and it is in the cut-off state, just like an off switch. Using the switching characteristics of diodes, various logic circuits can be formed.

4. Zener diode

It is made by using the reverse breakdown characteristics of diode. The voltage at both ends of the circuit remains basically unchanged, playing a role in stabilizing the voltage. It is a product that replaces the voltage stabilized electronic diode. The diffused or alloy silicon diode is a diode with rapidly changing reverse breakdown characteristic curve, which is used as control voltage and standard voltage.

5. Schottky diode

A diode with a "metal semiconductor junction" having Schottky characteristics. Its forward starting voltage is low. In addition to materials, the metal layer can also be made of gold, molybdenum, nickel, titanium and other materials. Its semiconductor material is silicon or gallium arsenide, mostly N-type semiconductor. This device is conductive by most carriers, so its reverse saturation current is much larger than that of PN junction conductive by a few carriers. Because the storage effect of minority carriers in Schottky diode is very small, its frequency response is only limited by RC time constant, so it is an ideal device for high frequency and fast switching.

6. Transient voltage suppression diode

It can provide fast overvoltage protection for circuits, including bipolar type and unipolar type.