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Monday, May 8, 2017

Basic Concepts of Amplifier CKT

Introduction:

The collective abbreviation of the two English words 'transfer' and 'resistor' is the transistor.

It basically works on the Resistance Transfer rule. The transistor is called a current driven device. And this current is transfer by resistance. That's why the name of the device is transfer resistor or transistor. Transistor is formed when connecting two Semi-conductor diodes as well. Transistor has three Regions (or Layers) and three terminals or electrodes or leads. The terminals are: collector, base and emitter.

Three scientists of America's Bell Telephone Laboratory invented transistor in 1948. There was a Revolution in the electronic world after the transistor was created.


Picture: John Bardeen, William Shockley and Walter Brattain at Bell Labs-1948


Transistor is the active device. Transistors are usually used for amplification and switching. Transistor has two PN Junctions. Every PN junction has a potential barrier.

Due to the barrier of the transistor, the input supply/signal is not transmitted instantly. As a result, the complete signal is not amplifiable; the part of the original signal is excluded. Particular part of the signal is a major drop in the gap between the faithful operations. To avoid this error and difficulty, the transistor has to be biased. This means that when crossing the signal through a transistor circuit, the circuits have to be biased to maintain the value of the zero signal collector current and collector emitter voltage.


Fig: PNP & NPN Transistor Symbol

Conditions of  biasing are: (1) Base emitter junction forward biasing and (2) Base collector Junction reverse biasing is done.

When the transistors send a small signal to the magnified size of the Output, then it is called amplification.The device is called Amplifier. So Transistor is one kind of Device that works as an amplifier & switching.

Amplifier:
The method in which the weak signal is changed into a strong signal, it is called amplification. The device that is used to amplify the amplification process is called an amplifier.

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