Chapter 14, Problem 14.3EP

For a noninverting amplifier, the resistances are $R_2=99\text{k}\Omega$ and $R_1=1\text{k}\Omega$ . The op−amp properties are: $A_{OL}={10}^4$ , $R_i=40\text{k}\Omega$ , and $R_o=0$ .Determine the closed−loop input resistance. (Ans. $R_{if}=4.04\text{M}\Omega$ )