negative feedback (NFB)
Negative feedback is one of several principles of feedback, another is positive feedback. In negative feedback, part of the output signal of an active quadripole is added inverted to the input signal at the quadripole input. In positive feedback, there is a subtraction of the feedback output signal, which is added to the input signal as a signal in phase.
In negative feedback, the effective input signal results from the subtraction of the actual input signal and the feedback signal, which in turn is formed from the output signal and the feedback factor. It is irrelevant for the consideration whether it concerns a local negative feedback of a single amplifier stage, or one which reaches over several or all amplifier stages.
This electronic circuit technique is used, among other things, in automatic control systems to prevent overloads, for example in automatic gain control( AGC) or automatic frequency control( AFC).