We are very familiar about the word “amplifiers” but we can not state where it is used. We are familiar about mike and speakers. We speak on mike in our own voice and Sound is heard loud on speakers with very less distortion. How do speakers make sound very loud?

It is because of using transistors as a function of amplifiers.Transistors used to magnify sound are known as Audio Amplifiers. Many transistors can be used in audio amplifiers, based on how loud sound is required. If only one transistor is used, it is known as single stage amplifier. Amplifier's name is given according to number of transistors used.

In electronic circuit, transistors used are known as electronic amplifiers. Common-emitter configuration is mostly used in amplifier circuits. Like audio amplifiers, many stages of transistors are used in electronic amplifiers, according to the strength of amplification required.

To design a simple amplifier, Power supply, transistors,capacitors and resistors are needed. R1, R2, Rc and Re are Resistors and choosing correct value for each resistor is very worthful in the first step of designing amplifier. Cin and Cout are capacitors to block DC voltage. Input is given between in the terminal of base and output is taken at collector terminal. The whole circuit is driven by DC power supply. A transistor is operated in linear region between cutoff and saturation regions.