Chapter: Electronic Circuits : Feed Back Amplifiers
Feed Back Amplifiers - Introduction
FEED BACK AMPLIFIERS
INTRODUCTION
A practical amplifier has a gain of nearly one
million i.e. its output is one million times the input. Consequently, even a
casual disturbance at the input will appear in the amplified form in the
output. There is a strong tendency in amplifiers to introduce hum due to sudden
temperature changes or stray electric and magnetic fields. Therefore, every
high gain amplifier tends to give noise along with signal in its output. The
noise in the output of an amplifier is undesirable and must be kept to as small
a level as possible. The noise level in amplifiers can be reduced considerably
by the use of negative feedback i.e. by injecting a fraction of output in phase
opposition to the input signal. The object of this chapter is to consider the
effects and methods of providing negative feedback in transistor amplifiers.
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