Pattrick Savarna is an associated co-author

Invented by Bell Labs, in 1947, a transistor is a solid-state electronic device which is used to regulate the electricity flow. Basically, it is a semiconductor device which consists of three-four layers. Some basic functions like amplifying a signal or opening/closing a circuit is attributed to it.

There are two types of standard transistors, NPN and PNP, with different circuit symbols.

Its Importance :

The contemporary computer culture has not been at its peak without the invention of transistor. Prior to the advent of this ultra sophisticated electronic active device, all the digital circuits came with vacuum tubes.

Thus the circuits were full of many flaws and drawbacks. Their larger size needed a bigger amount of energy. It used to get heated too early leading to its premature destruction. This led to the increased inefficiency of computers.

However, the transistor gave the computers a lifeline. It became an unavoidable part of the computer mechanism. Thus in any modern computer more than a million transistors can be found.

Bipolar Transistor

As the name suggests, the bipolar transistor, made of silicon, carries two polarities; n-type and p-type. Thus in a bipolar transistor, the current passes through negative polarity and positive polarity found in the layers made of semiconductors.

Field Effect Transistors

FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with the dual-carrier-type operation of bipolar (junction) transistors (BJT).

It can have many types and all are used in different fields and for various purposes. For example ; MOS FETS are used in the digital ICs of microcomputers. While, GaAs FETs are used in satellite broadcasting receivers where these transistors amplify the microwave. At last, the junction type FETs are suitable for any audio equipment's analog circuit.

Determining Size and Shape

Two factors ; the degree of power consumption and the method of mounting ensure the size and shape of any transistor.

Power Dissipation of a Transistor

A transistor which maximum collector power dissipation is less than IW is called a small-signal transistor. However, if any transistor which maximum collector power dissipation is more than 1W or equal is called a power transistor. Also a small-signal transistor has very low maximum collector current( 500mA) compared to the same of a power transistor.

Transistor as an Amplifier

A transistor, while working as an amplifier, uses a small amount of electricity. This small amount of energy is used to control the gate of a comparatively larger supply of electricity. The three basic parts( the base, the collector and the emitter) of a transistor do their assigned work to regulate electric supply. For an electric supply, especially a larger one, the base works as a gate controller device. Then the collector is what we say is the larger electrical supply. And as the name suggests, the emitter is what we get the regulated power from. This system needs a very meager amount of electricity.

Transistor as a Switch

Also a transistor works as a switch or a binary code for a digital processor. The same three basic parts of a transistor work here to do so. The only difference is that the transistor, unlike using low electricity as for amplifiers, here uses some higher amount of voltage. More clearly, when the switch goes on it needs five volts while it needs less than five volts when it goes off.