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What is a transistor?

A transistor is a miniature semiconductor that regulates or controls current or voltage flow in addition to amplifying and generating these electrical signals and acting as a switch or gate for them. Typically, transistors consist of three layers, or terminals, of a semiconductor material, each of which can carry a current.

Transistors are crucial components of modern electronics. When working as an amplifier, a transistor transforms a small input current into a bigger output current. As a switch, it can be in one of two distinct states -- on or off -- to control the flow of electronic signals through an electrical circuit or electronic device.

Why transistors are important?

A transistor has only one circuit element. In small quantities, transistors are used to create simple electronic switches. They're the basic elements in integrated circuits (ICs), which consist of a large number of transistors interconnected with circuitry and baked into a single silicon microchip.

In large numbers, transistors are used to create microprocessors where millions of transistors are embedded into a single IC. They also drive computer memory chips and memory storage devices for MP3 players, smartphones, cameras and electronic games. Transistors are embedded in nearly all ICs, which are part of every electronic device.

Transistors are also used for low-frequency, high-power applications, such as power-supply inverters that convert alternating current into direct current. Additionally, high-frequency applications use transistors, such as the oscillator circuits that generate radio signals.

List of some of the benefits of transistors.
Transistors have many benefits, from amplifying signals to requiring low-voltage supplies to being highly suitable for low-power applications.
How transistors revolutionized the tech world
Transistors were invented at Bell Laboratories in 1947. These solid-state devices rapidly replaced the bulky vacuum tube as an electronic signal regulator. The invention of the transistor fueled the trend to miniaturize electronics. They're now considered one of the most significant developments in the history of the PC.

Transistors are smaller, lighter and consume less power than vacuum tubes. As a result, electronic systems made with them are also smaller, lighter, faster and more efficient than ones made with vacuum tubes. Transistors are also stronger, require less power and, unlike vacuum tubes, don't require external heaters.

As the size of transistors decreased, their costs fell, creating more opportunities to use them. Integrating transistors with resistors and other diodes and electronics components makes ICs smaller. This miniaturization relates to Moore's Law, which states that the number of transistors in a small IC would double every two years.

Graphic listing number of transistors on different sizes of integrated circuits.
Blending transistors and diodes with resistors, capacitators and other components produces integrated circuits.
Transistors explained
A semiconductor device, which conducts electricity in a semi-enthusiastic way, falls somewhere between a real conductor like copper and an insulator such as the plastic wrapped around wires. Although most transistors are made from silicon, they also use other materials such as germanium and gallium arsenide.

Silicon, a chemical element often found in sand, isn't normally a conductor of electricity. A chemical process called doping introduces impurities into a semiconductor to modulate electrical, optical and structural properties. This enables silicon to gain free electrons that carry electric current. The silicon becomes either an n-type semiconductor where electrons flow out of it or a p-type semiconductor where electrons flow into it. Either way, the semiconductor enables the transistor to function as a switch or amplifier.

A transistor's three-layer structure contains one of the following layers: