BC140, NPN transistor

An NPN transistor is a bipolar junction transistor (BJT). It is operated with an electric current and is used for switching and amplifying signals without using mechanically moving parts.

There are two types of BJTs: NPN and PNP. The letters indicate the order and doping type of the layers. Essentially, a BJT constitutes two p-n junctions connected together in series (like that of a p-n diode.) The three terminals are called collector (C), base (B) and emitter (E).

Adjustable parameters

Designation Range Default value
Forward current gain 0.1 ... 1000 120
Reverse current gain 0.1 ... 1000 1
Saturation current 1e-16 ... 1e-3 A 8.81138e-14
Forward early voltage 1 ... 1000 V 64