Strictly speaking, transistor generally refers to all single components based on semiconductor materials, including a variety of semiconductor materials made of diode (two terminals), triode, field effect tube, thyristor (the last three are three terminals) and so on. Transistors sometimes refer to more than a transistor transistor. Three terminal transistors fall into two main categories: bipolar transistors (BJTS) and field effect transistors (FETs, unipolar). A transistor has three poles (terminals); The three poles (terminals) of bipolar transistor are respectively Emitter, Base and Collector composed of N-type and P-type semiconductors. The three terminals of a field-effect transistor are Source, Gate, and Drain.

Transistor because there are three electrodes, so there are three ways to use, respectively, emitter grounding (also known as common emitter amplification, CE configuration), base grounding (also known as common base amplification, CB configuration) and collector grounding (also known as common set amplification, CC configuration, emitter with coupling).

Due to their fast response speed and high accuracy, transistors can be used for a wide variety of digital and analog functions, including amplification, switching, voltage stabilization, signal modulation and oscillators. Transistors can be packaged individually or in a very small area that can hold 100 million or more transistors as part of an integrated circuit.