What is a bipolar transistor, its structure, classification, and basic principles 1

Bipolar Junction Transistor (BJT) is a semiconductor device that is currently one of the most widely used electronic devices. It is composed of three regions, namely P-type region, N-type region, and P-type region, abbreviated as PNP transistor or NPN transistor. BJTs can serve as current amplifiers, switches, BAS21 oscillators, and are widely used in electronic circuits.

Composition and structure of BJT

BJT consists of three regions, namely P-type region, N-type region, and P-type region (PNP Transistor) or N-type region, P-type region, and N-type region (NPN transistor). The junction between the P-type region and the N-type region is called a PN junction, and the two ends of the PN junction are connected to the P-type region and the N-type region, respectively. There is a potential barrier on the junction surface of the PN junction. When the PN junction is in a forward biased state, the potential barrier decreases and electrons and holes can flow; When the PN junction is in a reverse biased state, the potential barrier increases and electrons and holes cannot flow.

Classification of BJTs

BJTs can be divided into two types: PNP transistors and NPN Transistor. Among them, the P-type region of the PNP transistor is the base, the N-type region is the emitter, and the P-type region is the collector; The N-type region of an NPN transistor is the base, the P-type region is the emitter, and the N-type region is the collector.