feedback amplifiers

The connection circuit in a closed loop such that a portion of the output is fed back to the input is called a feedback network.The feedback in which the output when applied to the input diminishes the output is called as negative feedback.



















A feedback amplifier therefore may be positive feedback or negative feedback depending on whether the output when fed back to the input enhances or decreases the output.

Classification of feedback amplifier :\

1.Voltage amplifiers:\
The voltage amplifiers have voltage output proportional to the input voltage signal and the proportionality factor is irrespective of the input source resistance and load resistance.

Voltage series amplifier has input terminals across a voltage source and output is drawn across the load resistance.



2. Current series feedback:
The output voltage is directly proportional to the input currenthe proportionality factor is irrespective of the source and load resistances.



3.Voltage shunt feedback:
The output cuurent is directly proportional to the input voltage.


4.Current shunt feedback:
The input and output current are in direct proprtion and the proptionality factor is independent of Rs and Rl.



An important table is given below: