Closed Loop Gain
Before we discuss the closed-loop gain, let’s review a concept: transfer function. A transfer function is a mathematical representation of the relation between the input and output of a system.
The transfer function of a closed-loop configuration is G = A / (1 + βA), which is the closed-loop gain, where A is open loop gain, β is feedback factor, βA is loop gain. It is easy to see the difference between closed loop gain and open loop gain.