A transistor is a device that acts as a switch or gate for electronic signals and regulates the flow of current and voltage. This device consists of three layers of semiconductors that carry current. In the year 1947, three scientists invented transistor in Bell Laboratories. It replaced the vacuum tube to serve the purpose of an electronic regulator. Moreover, in future, it paved a way for cheaper and smaller calculators, radios and computers. The transistor is a basic element in almost all electronic devices.

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There are two types of transistors – Junction transistor and Field-Effect transistor.


Functions Of Transistor-

(1) It is used as a switch for “large currents”

You can turn ON/OFF a large current flow by turning ON/OFF a small current using a transistor. Turning ON/OFF a large current flow directly without a transistor will be a difficult task and might need the person to manually cut off the line.

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(2) It is used for amplification

For example, If you can manipulate the “small current” wave shape to follow that of a sound signal (by converting sound to electrical signal), and then apply to the transistor, the “large current” will get the shape of that of the “small current” which in turns is the amplified sound signal shape. In short, sound signal (for that matter any signal) is amplified with the help of a transistor.

Working of a transistor-