What is Closed loop; loop gain? — Physics

Definition 9.1 University Physics — Year 2 · Chapter 9 — Electronics: Feedback, Oscillators and Signal Acquisition

An amplifier of transfer function $\underline A(\jmath\omega)$ receives the input $\underline e$ plus a fraction $\underline\beta(\jmath\omega)\,\underline s$ of its own output $\underline s$ (positive feedback; for negative feedback change the sign of $\beta$ ). The closed-loop transfer function and the loop gain are

\underline H = \frac{\underline s}{\underline e} = \frac{\underline A}{1 - \underline A\,\underline\beta} , \qquad \underline T = \underline A\,\underline\beta .

Read in context →