Diodes are electronic devices made of semiconductor materials (silicon, selenium, germanium, etc.). It is the first semiconductor device with unidirectional conduction and rectification function in the world.

There are many kinds of diodes, which are mainly used in electronic circuits and industrial products. After years of unremitting efforts by scientists, the application of semiconductor diodes is gradually popularized, and the application scope of light-emitting diodes is also gradually expanded. It is a light source that meets the requirements of green lighting and is incomparable to ordinary light-emitting devices.

Diode consists of PN junction, corresponding electrode leads and package.

Using different doping processes, P-type semiconductor and N-type semiconductor are made on the same semiconductor (usually silicon or germanium) by diffusion, and a space charge region is formed at their interface, which is called PN junction.

The electrode drawn from the P region is called anode, and the electrode drawn from the N region is called cathode. Due to the unidirectional conductivity of the PN junction, when the diode is on, the current direction is from the anode to the cathode through the tube.

The diode has two electrodes, and the electrode drawn from the P region is the positive electrode, also called the anode; The electrode drawn from the N region is the negative electrode, also called cathode. The direction of the triangle arrow indicates the direction of the forward current, and the character symbol of the diode is denoted by VD. The main principle of diode is to use the unilateral conductivity of PN junction, add leads and packaging on PN junction to form diode.