What is a transistor, the principle, application, and historical development of transistors 2

When a forward voltage is applied between the base and emitter, the electrons at the emitter will move towards the base, while an electric field is formed between the base and collector, accelerating the electrons in the collector and generating a collector current. When a reverse voltage is applied between the base and emitter, electrons in the emitter cannot move towards the base direction, and therefore cannot form a base current, making it impossible to control the magnitude of the collector current.

3、 Types of transistor

transistor  are classified into various types based on their working principles and structures, among which commonly used ones include bipolar junction transistors (BJTs), field-effect transistors (FETs), and bipolar field-effect transistors (BGFETs).

1. Bipolar Transistor (BJT)

Bipolar transistor is a three-layer semiconductor device composed of an n-type semiconductor and a p-type semiconductor, with a very thin layer of p-type semiconductor sandwiched in between. These three layers are called the emitter, base, and collector, respectively. The working principle of BJT is to use an external voltage to control the base current, which in turn controls the magnitude of the collector current.

There are two types of BJTs, namely npn type and pnp type. In npn type BJTs, the emitter is an n-type semiconductor, the base is a p-type semiconductor, and the collector is an n-type semiconductor. In PNP BJTs, the emitter is a p-type semiconductor, the base is an n-type semiconductor, and the collector is a p-type semiconductor.transistor