Q.Explain the terms feedback factor, loop gain and closed loop gain.

These three quantities describe how much of the output is fed back, how strong the feedback loop is, and what gain results.

[!ANSWER]

Feedback factor $\beta = V_f/V_o$ is the fraction of output returned to the input; loop gain $A\beta$ is the product of open-loop gain and feedback factor; closed-loop gain $A_f = V_o/V_s = A/(1+A\beta)$ is the overall gain with feedback.

[!TLDR]

Feedback factor $\beta = V_f/V_o$; loop gain $= A\beta$; closed-loop gain $A_f = V_o/V_s = A/(1+A\beta)$.

In a feedback amplifier a fraction of the output is sampled and returned to the input. Three terms describe this action.

Feedback factor (feedback ratio / feedback fraction), $\beta$: it is the ratio of the feedback voltage to the output voltage,

It tells us what fraction of the output is fed back, and is fixed by the passive feedback network.

Loop gain, $A\beta$: it is the product of the amplifier's open-loop gain $A$ and the feedback factor $\beta$. It represents the gain experienced by a signal in going once around the feedback loop (amplifier then feedback network), and it decides how strongly feedback modifies the amplifier.

Closed-loop gain, $A_f$: it is the overall gain of the amplifier with feedback connected,

for negative feedback. It is smaller than the open-loop gain $A$ but far more stable.

[!ANSWER]

Feedback factor $\beta = V_f/V_o$ (fraction of output fed back); loop gain $= A\beta$ (gain around the loop); closed-loop gain $A_f = V_o/V_s = A/(1+A\beta)$ (overall gain with negative feedback).