What is a Transistor and How Does it Work?

3 minute read
What is a Transistor

The transistor is considered the greatest invention of the 20th century. It replaced vacuum tubes as it functioned more efficiently. It consumed less power and was highly efficient in small circuits. Find out who invented Transistors, how do they work, and what are the benefits of using them!


It is an electronic device made of three layers of semiconductors material that can act as an insulator and conductor. It used to amplify or switch electronic signals and electrical power. The words trans mean transfer property and istor mean resistance property offered to the junctions. In other words, it is a switching device that regulates and amplifies electrical signals like voltage or current.

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Parts in a Transistor

It is made up of three layers of semiconductor materials or more specifically terminals which help to make a connection to an external circuit and carry the current. A voltage or a current that is applied to any pair of the terminals of a transistor controls the current through the other pair of terminals. There are three terminals for a transistor. (Tramadol) Here are all the three terminals you should know:

  • Base: This is used to activate the transistor
  • Collector: It is the positive lead of the transistor
  • Emitter: It is the negative lead of the transistor

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Transistor Symbols

Want to know about the symbols? There are two types of transistor symbols. Here are two symbols in detail that will help you understand better:

  • NPN transistor- It has two blocks of n-type semiconductor material and one block of P-type semiconductor material is known as an NPN transistor.
  • PNP transistor- If the material has one layer of N-type material and two layers of P-type material then it is called a PNP transistor.
Credits: Component101

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Who Invented the Transistor?

The transistor was successfully demonstrated on December 23, 1947, at Bell Laboratories in Murray Hill, New Jersey. Bell Labs is the research arm of American Telephone and Telegraph (AT&T). The three individuals credited with the greatest invention of the 20th century were William Shockley, John Bardeen, and Walter Brattain.

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The characteristics of the transistor are that it can represent the relation between the current and the voltage of it in a particular configuration. Here are all the characteristics:

  • Input characteristics: It will give us the details about the change in input current with the variation in input voltage by keeping output voltage constant.
  • Output characteristics: It is a plot of output current with output voltage by keeping the input current constant.
  • Current transfer Characteristics: This plot shows the variation of output current with the input current by keeping the voltage constant.
Credits: Sachin Sir Physics

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Working Principle

It is a current-driven device where two P-N junctions exist within a BJT. One P-N junction exists between the emitter and base region and the second junction exists between the collector and base region. A very small amount of current flow through the emitter to the base can control a reasonably large amount of current flow through the device from the emitter to the collector.

In the usual operation of BJT, the base-emitter junction is forward-biased and the base-collector junction is reverse-biased. When a current flows through the base-emitter junction, a current will flow in the collector circuit. In order to explain the working of the transistor, let us take an example of an NPN. The same principles are used for PNP except that the current carriers are holes and the voltages are reversed.

Credits: Veritasium

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