Practical Electronics/Transistors


Simple transistor
Transistors inside Intel CPU

Transistors are a solid state bi-junction device that can be used to amply voltage or current.Every transistor has three terminals: Base, Emitter, and Collector which form two junctions area namely BE and CE.

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 TransistorEdit

Bbipolar transistor have 2 types of transistor namely PNP and NPN types.
NPN Transistor: One positively charged semiconductor between two negatively charged semiconductors. PNP Transistor: One negatively charged semiconductor between two positively charged semiconductors. There are 3 leads called base (B) , collector (C) and emitter (E)

Transistor Construction Circuit's Symbol Looks
NPN Transistor      
PNP Transistor      

Field Effect TransistorEdit

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

Applications of TransistorsEdit

Transistors can be used as electronic switches and audio amplifiers.


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