The transistor is a solid-state component that uses a small current to control the flow of a large current. It is used mainly in amplification, detection, and switching.

The transistor is one of the most important inventions of modern times. They are smaller, cheaper, and use less power than the vacuum tubes they replaced. Without transistors, the modern computer age would not be possible.

History of the Transistor

The transistor was invented in 1947 by three Americans at Bell Laboratories: John Bardeen, Walter Brattain, and William Shockley. They were trying to invent a new telephone amplifier and invented the transistor almost by accident. In 1956, they were awarded the Nobel prize in physics for their discovery.

Vacuum Tubes

Before transistors, vacuum tubes (electron tubes) were used. Similar to a light globe, they have several conductors vacuum-sealed inside a glass tube. They were bulky, expensive, and failed often. They also used a lot of energy because the cathode filament was heated.

Types of Transistor

There are many types of transistor, the main ones being the bipolar junction transistor (BJT) and the field-effect transistor (FET).

The bipolar junction transistors has three terminals: collector, base, and emitter. They are used as switches and signal amplifiers, and are commonly packaged in small plastic or metal cases with the three terminals on one end.

The field-effect transistor has four leads: source, gate, drain, and body. The most common FET is the MOSFET, or metal-oxide-semiconductor field-effect transistor. They are commonly used inside integrated circuits as switches.

Parts of a Transistor

Bipolar junction transistors have three leads connected internally to two semiconductor junctions. As the voltage rises in the base terminal, the current flowing between the emitter and collector terminals increases. At this stage, the transistor is behaving as an amplifier for the base signal.

As the base voltage is increased, a point is reached where no more current will flow. This is called the saturation state, and the transistor is now behaving like a closed switch.

Uses for Transistors

Transistor are found in practically every electrical device more complicated than a light bulb. There are hundreds inside every radio and television, and computer chips have millions of transistors etched onto a tiny piece of silicon.