Sensitivity of a closed loop system for a change in the system gain is 1/(1+GH)

In a closed loop system the gain without the feed back loop being closed is called open loop gain!!!

e.g if forward gain is "A" and feed back factor is "B"

then open loop gain is "AB"

and closed loop gain will be [A/(A+B)]

Feedback oscillators have a closed loop gain of

closed loop system

The formulas of a unity-feedback loop are:

1. Closed-loop transfer function: This is the ratio of the output of the system to its input in the closed-loop configuration. It is calculated by dividing the open-loop transfer function by (1 + open-loop transfer function).
2. Closed-loop gain: This is the gain of the system in the closed-loop configuration and represents the amplification of the input signal in the system. It is calculated by multiplying the open-loop gain by (1 + open-loop gain).
3. Closed-loop bandwidth: This is the frequency range over which the system can effectively respond to input signals in the closed-loop configuration. It is usually determined by the pole locations in the system's transfer function.