The transistor is made of two closely spaced PN junctions on a semiconductor substrate. The two PN junctions divide the whole semiconductor into three parts, the middle part is the base region, and the two sides are the emitter region and the collector region. Both PNP and NPN.

 

Corresponding electrodes are drawn from the 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 thicker and the impurity concentration is high. The emitter region of the PNP transistor "emits" holes, and its moving direction is consistent with the direction of the current, so the emitter arrow points inward; the emitter region of the NPN transistor "emits" " are free electrons, which move in the opposite direction of the current, so the emitter arrows outward. The emitter arrow points to also the conduction direction of the PN junction under forward voltage. There are two types of silicon transistors and germanium transistors, PNP type and NPN type.

 

The package form and pin identification of the triode

 

The commonly used package forms of triodes are metal package and plastic package. The arrangement of the pins has a certain pattern. The bottom view is placed so that the three pins form the vertices of an isosceles triangle. From left to right, it is e b c. ; For small and medium-power plastic triodes, make the plane face to itself, and place the three pins downward, then e b c from left to right.

 

There are many kinds of various types of transistors in China, and the arrangement of the pins is not the same. If you are not sure about the arrangement of the pins in use, you must measure to determine the correct position of each pin, or look up the transistor manual to clarify the transistor. Characteristics and corresponding technical parameters and information.