Transistor

Simple transistor

Transistors inside Intel CPU

It was first invented in 1947 in the United States of America by a three-man team of Bardeen, Shockley, and Brattain at Bell's Telephone Lab. The transistor is the wonder device that becomes the most important building block in all types of circuits today and it is responsible for miniaturization of circuits from the previous uses of the large vacuum tubes. Transistor is used mainly as electronic switches to control the flow of currents.

Earlier during the introduction of the transistor, it is used singly inside all types of circuits such as shown on the left picture but in this modern age, even the simplest of IC may consist hundred of thousands of transistors inside the circuits. The CPU chips shown on right are believed to have thousands of billions of transistors squeezed inside the area just larger than the thumb area.


There are two kinds of transistors namely:

1. Bipolar Transistors
2. Field Effect Transistors

The bipolar transistor is invented in 1947 first and the unipolar transistor (a later invention) is named as the field-effect transistor (FET).

Bipolar Transistor

Bbipolar transistor have 2 types of transistor namely PNP and NPN types.
There are 3 leads called base (B) , collector (C) and emitter (E)

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  Symbol of PNP transistor
• 
  Symbol of NPN transistor

Field Effect Transistor

There are 2 main types of FET namely junction gate FET (JFET / JUGFET) or metal oxide FET (MOSFET)

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  Current flow through n-channel JFET
• 
  Structure of basic MOSFET

Applications of Transistors

Transistors can be used as electronic switches and audio amplifiers.

References

Teach Yourself Electronics First Edition:1975 (Malcolm Plant) ISBN 0-304-42230-0