When some part of output signal is again fed back to input then that signal is called as feedback signal.If the feedback signal and input signal are in phase means they have same polarities the feedback is said to be positive. If the feedback and input signal are out of phase then the feedback is said to be negative. The figure below shows basic block diagram of negative feedback.

Negative feedback has following advantages:

• The negative feedback reduces noise

• It has less frequency distortion means improved frequency response

• Better stabilized voltage gain

• It has less harmonic distortion.

• It has less amplitude distortion.

• It has less phase distortion.

• Input and output impedances can be modified as desired.

• It can increase or decrease output impedances.

• It has higher fidelity i.e. more linear operation