A transistor is a type of semiconductor device

A transistor is a semiconductor device used to amplify or switch electrical signals and power. Transistors are one of the fundamental components of modern electronic products. It is composed of semiconductor materials and typically has at least three terminals for connecting electronic circuits. The voltage or current applied to one pair of terminals of a transistor controls the current passing through another pair of terminals. Due to the possibility of controlled (output) power being higher than controlled (input) power, transistors can amplify signals. Some transistors are individually packaged, but more transistors are embedded in integrated circuits.

Most transistors are made of very pure silicon, some are made of germanium, but sometimes other semiconductor materials are also used. Transistors may only have one type of charge carrier in field-effect transistors, or there may be two types of charge carriers in bipolar junction transistor devices. Compared to vacuum tubes, transistors are usually smaller in size and require less power to operate. Some vacuum tubes outperform transistors at very high operating frequencies or high operating voltages. Many types of transistors are manufactured by multiple manufacturers according to standardized specifications.