Basic Principle of Transistor

How does a Transistor works.........?

There are two main types of transistors-junction transistors and field effect transistors. Each works in a different way. But the usefulness of any transistor comes from its ability to control a strong current with a weak voltage. For example, transistors in a public address system amplify (strengthen) the weak voltage produced when a person speaks into a microphone. The electricity coming from the transistors is strong enough to operate a loudspeaker, which produces sounds much louder than the person's voice.

JUNCTION TRANSISTORS

A junction transistor consists of a thin piece of one type of semiconductor material between two thicker layers of the opposite type. For example, if the middle layer is p-type, the outside layers must be n-type. Such a transistor is an NPN transistor. One of the outside layers is called the emitter, and the other is known as the collector. The middle layer is the base. The places where the emitter joins the base and the base joins the collector are called junctions.

History Of Electronics

         The history of electronics is a story of the twentieth century and three key components—the vacuum tube, the transistor, and the integrated circuit. In 1883, Thomas Alva Edison discovered that electrons will flow from one metal conductor to another through a vacuum. This discovery of conduction became known as the Edison effect. In 1904, John Fleming applied the Edison effect in inventing a two-element electron tube called a diode, and Lee De Forest followed in 1906 with the three-element tube, the triode. These vacuum tubes were the devices that made manipulation of electrical energy possible so it could be amplified and transmitted.