What is a bipolar transistor, its characteristics, principles, classification, operating procedures, and development trends 1

Bipolar Junction Transistor (BJT) is a type of semiconductor transistor that belongs to the category of triodes and has two PN junctions. It is composed of three semiconductor layers doped with different materials, with two P-type semiconductor layers sandwiched between an N-type semiconductor layer. The main function of this device is to amplify and switch current, and it is widely used in various electronic devices and circuits.

Characteristics of bipolar transistors:

(1) High gain: Bipolar transistors have a high current amplification factor, usually between a few hundred to several thousand, which can amplify weak signals and increase the signal level.

(2) Good high-frequency characteristics: Bipolar transistors have excellent performance in the high-frequency range and can operate in the frequency range of tens of GHz.

(3) Good stability: The working characteristics of bipolar transistors are relatively stable and not easily affected by environmental factors such as temperature and voltage.

(4) Easy to control: The control voltage and current of bipolar transistor are relatively easy to control, and their working state can be adjusted by adjusting the control voltage and current.

The principle of bipolar transistor:

The principle of the bipolar transistor LF347N is based on the characteristics of the PN junction, which has two conduction states: forward and reverse. When the PN junction is forward biased, current can flow from the P region into the N region, forming diffusion of minority carriers; When the PN junction is reverse biased, the resistance of the PN junction is very high and almost non-conductive due to the obstruction of the diffusion of minority carriers.