A transistor is a semiconductor device that can be used to amplify or switch electrical signals and power. It is one of the basic building blocks of modern electronics and is composed of semiconductor material, usually with at least three terminals. The three terminals of a transistor are:
- Emitter: This is the transistors negative lead.
- Base: This is the terminal that activates the transistor.
- Collector: This is the terminal that collects the current that flows through the transistor.
A transistor can use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals, a property called gain. It can produce a stronger output signal, a voltage or current, proportional to a weaker input signal, acting as an amplifier. It can also be used as an electrically controlled switch, where the amount of current is determined by other circuit elements. There are two main types of transistors: bipolar and field-effect. Transistors are commonly used in digital circuits as electronic switches which can be either in an on or off state, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates.
