Classification and structure of transistor

The structure of a transistor. It consists of an emitter junction, a collector junction, and N-type and P-type semiconductors, with three electrodes: base (B), emitter (E), and collector (C). For PNP type transistors, they are composed of two P-type and one N-type semiconductors, while for NPN type semiconductors, they are composed of two N-type and one P-type semiconductor. The part formed at the junction of P-type and N-type semiconductors is called a PN junction, the PN junction between the base and collector is called a collector junction, and the pN junction between the base and emitter is called an emitter junction.

There are many types of transistor, and there are also various classification methods. Classified by purpose, frequency, power, material, etc. 1) NPN and PNP transistors made of silicon materials are classified by material and polarity NPN and PNP transistors made of germanium material. 2) There are high and medium frequency amplifying tubes, low-frequency amplifying tubes, low-noise amplifying tubes, phototubes, switching tubes, high back pressure tubes, Darlington tubes, and transistors with damping according to their applications. 3) According to power, there are low-power transistors, medium power transistors, and high-power transistors. 4) According to the operating frequency, there are low-frequency transistors, high-frequency transistor, and ultra-high frequency transistors. 5) According to the manufacturing process, there are flat type transistors, alloy type transistors, and diffusion type transistors. 6) According to the different packaging types, they can be divided into metal encapsulated transistors, glass encapsulated transistors, ceramic encapsulated transistors, plastic encapsulated transistor, etc.