Chapter 12, Problem 12.3EP

(a) A feedback amplifier has an open-loop low-frequency gain of $A_O=5\times {10}^4,$ an open-loop bandwidth of ${\omega }_H=(2\pi )(5)\text{rad}/\text{s},$ and a closed-loop low-frequency gain of $A_f(0)=80.$ Determine (i) $\beta$ and (ii) the closed-loop bandwidth. (b) Using the results of part (a), if $\beta$ is reduced by 50 percent, determine the percent change in (i) $A_f(0)$ and (ii) ${\omega }_{fH}?$ (Ans. (a) (i) $\beta =0.01248$ , (ii) ${\omega }_{fH}=(2\pi )\left(3.125\times {10}^3\right)\text{rad}/\text{s};(\text{b})(\text{i})+100\%,\text{ (ii) }-50\%)$