feedbackkrets

Feedbackkrets, or feedback circuit, is a circuit arrangement in which a portion of the output signal is returned to the input to influence the input signal. The main purpose is to control characteristics such as gain, bandwidth, linearity, stability, and noise. Feedback is a foundational concept in electronics and control theory and is used to enhance performance and manage dynamic behavior.

There are two primary types: negative feedback, where the fed-back signal is subtracted from the input, and positive feedback, where it is added. Negative feedback tends to stabilize gain, reduce distortion and noise, and can broaden bandwidth, while positive feedback can increase gain and, if not carefully controlled, cause oscillations or bistable behavior. Feedback strength is described by a factor β, and the system’s closed-loop gain depends on the open-loop gain A and β; in a typical negative-feedback model, the approximate closed-loop gain is A/(1 + AB).

Common implementations include op-amp configurations such as non-inverting and inverting amplifiers, where a feedback network sets the desired gain, and voltage followers that provide unity gain with high input impedance. Feedback also plays a central role in oscillators (positive feedback with the right phase shift) and in many control systems and signal-conditioning stages.

Design considerations include stability, phase margin, and noise performance. Proper feedback improves linearity, reduces distortion, and extends bandwidth, but can cause instability if loop gain and phase shift are not carefully managed.

History notes: negative feedback in amplifiers was popularized by Harold S. Black in the 1920s–1930s, leading to widespread use in electronic and control systems.