Consider the noninverting op-amp circuit in Figure P12.18. The input resistance of the op-amp is \(R_{i}=\infty\) and the output resistance is \(R_{o}=0\), but the opamp has a finite gain \(A\).

(a) Write the closed-loop transfer function in the form

\[A_{v f}=\frac{v_{o}}{v_{s}}=\frac{A}{(1+\beta A)}\]

(b) What is the expression for \(\beta\) ?

(c) If \(A=10^{5}\) and \(A_{v f}=20\), what is the required \(\beta\) and \(R_{2} / R_{1}\) ?

(d) If \(A\) decreases by 10 percent, what is the percent change in \(A_{v f}\) ?

Transcribed Image Text:

R2 www Rof Rif R www. +1 Figure P12.18