What are the properties of negative feedback in closed loop system?

They are commonly used in process, micro-computer and amplifier systems. In general feedback is the process by which a fraction of the output signal, either a voltage or a current, is used as an input. If this feed back fraction is opposite in value or phase to the input signal, then the feedback is said to be Negative Feedback, or sometimes degenerative feedback. Negative feedback opposes or subtracts from the input signals giving it many advantages in the design and stabilisation of control systems. For example, if the systems output changes for any reason, then negative feedback affects the input in such a way as to counteract the change. Feedback reduces the overall gain of a system with the degree of reduction being related to the systems open-loop gain. Negative feedback also has effects of reducing distortion, noise, sensitivity to external changes as well as improving system bandwidth and input and output impedances. Feedback in an electronic system, whether negative feedback or positive feedback is unilateral in direction. Meaning that its signals flow one way only from the output to the input of the system. This then makes the loop gain, G of the system independent of the load and source impedances. As feedback implies a closed-loop system it must therefore have a summing point. In a negative feedback system this summing point or junction at its input subtracts the feedback signal from the input signal to form an error signal, which drives the system. If the system has a positive gain, the feedback signal must be subtracted from the input signal in order for the feedback to be negative as shown. read less