Structure types of transistors

structure type

A transistor is made by fabricating two PN junctions that are very close to each other on a semiconductor substrate. The two PN junctions divide the entire semiconductor into three parts, with the middle part being the base region and the two sides being the emitter and collector regions. There are two arrangements: PNP and NPN.

Lead out corresponding electrodes from three regions, namely base b, emitter e, and collector c.

The PN junction between the emitter region and the base region is called the emitter junction, and the PN junction between the collector region and the base region is called the collector junction. The base region is very thin, while the emitter region is thick and has a high impurity concentration. The emitter region of a PNP transistor "emits" holes, which move in the direction of the current

Consistent, therefore the emitter arrow points inward; The emitter region of an NPN transistor emits free electrons, which move in the opposite direction to the current direction, so the emitter arrow is pointing outward. The direction of the emitter arrow is also the conduction direction of the PN junction under forward voltage. Silicon crystal

Both transistor and germanium crystal transistor have two types: PNP and NPN.

The packaging form and pin identification of transistors

The commonly used packaging forms of transistors include metal packaging and plastic packaging, and the arrangement of pins follows certain rules,

Place the bottom view position so that the three pins form the vertices of an isosceles triangle, with e b c from left to right; For small and medium power plastic transistors, place the plane facing themselves and the three pins facing downwards according to the diagram, and the order from left to right is e b c.

There are many types of transistors in China with different pin arrangements. For transistors with uncertain pin arrangements during use, measurements must be taken to determine the correct position of each pin, or the transistor user manual must be consulted to clarify the transistor's specifications

Characteristics and corresponding technical parameters and information.