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What is amplifier

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A transistor or thermionic valve based circuit capable of increasing the amplitude or power of an input signal is called amplifier actually speaking the amplification capacity of the transistor or valve is the base of amplifier the reception capacity of the earliest type of receivet was limted up to 40-80 KMS only triode was not invented at that time public address amplifiers and wide range reception capacity type radio receivers could only be made after  the invention of triode valve after knowing its amplification capability
A multi stage a,f amplifier (a.f. range_2hz to20 kHz) is used in public address amplifier which amplifies the a.f output of a microphone upto such a level  that a number of powerful loudspeakers can be operated simultaneously .in this way ,the
voice  of a person can be made  to reach thousands of listeners present in a large Stadium or in a field
In radio receiver .the microvoltage level r,f output of an aerial is converted into several volts r.f  signal by a r.f amplifier .this amplified r.f signal is then converted into a.f signal by employing a detector stage .the a.f amplifier stage of a receiver strengthens the a.f signal so as to drive the loud speaker
In this way ,the main component of a radio  or A TV  receiver and public address amplifier is the amplifier .the capacity of a radio receiver depends on the amplification technique used in it

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