Show that for the inverting amplifier if the op-amp gain is A, the input resistance is given by
*For this problem you will need to use an Op-Amp equivalent circuit model to get the correct answer. First derive expression for the Thevenin resistance from the node past the R1 resistor (to the right of the resistor R1). In other words, derive the expression R2/(1+A) first! Then move back to the left-hand side node of the resistor R1 and add it to the previous expression to get the final expression for the Thevenin's resistance. Assume Ri=infinity and Ro=0, for simplicity.

Show transcribed image textRin = R1+A +1 ,