Transistor
Transistor is a semiconductor device found in everything from radios to computers and all other modern electronics. It commonly used as an amplifier or an electrically controlled switch. Transistors are used in a wide variety of digital and analog functions, including amplification, switching, voltage regulation, signal modulation, and oscillators. Most transistors are based on the use of silicon.
There are two main categories of transistors. There are bipolar junction transistors (BJT) and field effect transistors (FET). Transistors are rarely used as discrete devices, almost always being incorporated in monolithic Integrated Circuits.