Question

The input resistance of the op-amp circuit shown is:

• A. \(100\ \text{k}\Omega\)
• B. \(1\ \text{k}\Omega\)
• C. \(99\ \text{k}\Omega\)
• D. \(101\ \text{k}\Omega\)

Hint:

In op-amp circuits, input resistance = external series resistance if connected to non-inverting terminal.

Answer 1

The Correct Option is B

The op-amp is in **non-inverting configuration**, but input voltage \(V_i\) is applied through a \(1\ \text{k}\Omega\) resistor directly to the non-inverting terminal. Since the op-amp has high input impedance, the effective input resistance seen by the source is just the resistance in series with the input, i.e., \(1\ \text{k}\Omega\).