Feedback Needs an Output

Feedback taken without knowing the specific outcome it will be used to adjust, is not feedback. It may be input of some sort, but for what system? What does it feed? To what does it link?

Below is a schematic of well-defined feedback. An operational amplifier is shown using feedback in order to produce output with a closed-loop gain of \(1 + \frac{R_f}{R_g}\). That is, \(V_{out} = (1 + \frac{R_f}{R_g})V_{in}\).

Operational amplifier noninverting

Feedback in a system needn’t be live like in the op amp above. There may be an asynchronous processing/integration step, but unambiguous links must be in place.