A transistor is a miniature discrete semiconductor device that can amplify, control, or generate electrical signals. Transistors typically consist of three electrical leads, each composed of a semiconductor material that can carry a current. In small quantities, transistors are used to create simple electronic switches, but more often they are used as the foundation of modern integrated circuits (ICs).
There are multiple parameters to consider when choosing a transistor for your application. Popular transistor types include bipolar (BJT), FETs and MOSFETs, to name a few. Designers and engineers must take into account voltage rating, current rating, gain, and total power dissipation, among others, making them more complex than resistors or capacitors.