Transistor, also known as semiconductor triode, also known as bipolar transistor, crystal triode, is a semiconductor device that controls current. Its function is to amplify a weak signal into an electrical signal with a larger amplitude, and it is also used as a contactless switch.

Transistor is one of the basic semiconductor components, which has the function of current amplification and is the core component of electronic circuits. The transistor is made of two PN junctions that are very close together on a semiconductor substrate. The two PN junctions divide the entire semiconductor into three parts, the middle part being the base region, and the two sides being the emission region and the collector region. The arrangement methods include PNP and NPN.