The structure and type of transistor

There are two types of transistors: bipolar and unipolar. Bipolar transistors are usually referred to as transistors, while unipolar transistors are referred to as field effect transistors.
A transistor is a semiconductor device, which consists of two PN junctions (emitter junction and collector junction) formed by three regions (emitter, base and collector) with different doping types and concentrations, which are led out from the three regions respectively Three electrodes (emitter e, base b, and collector c).
Transistors can be divided into NPN type and PNP type according to different doping types; according to the different semiconductor materials used, they can be divided into two types: silicon tube and germanium tube.
The characteristic of the internal structure of the transistor is that the doping concentration of the emitter region is much higher than the doping concentration of the base region, and the base region is very thin, and the area of ​​the collector junction is larger than the area of ​​the emitter junction. This is the internal condition for the transistor to have the ability to amplify.