Question

In the circuit shown, the op-amp has finite input impedance, infinite voltage gain and zero input offset voltage. The output voltage V_out is

(A) - I₂(R₁ + R₂)

(B) I₂R₂

(C) I₁R₂

(D) - I₁(R₁ + R₂)

Answer 1

Correct option (A) - I₂(R₁ + R₂)  

Explanation:

Given, Z_i = ∞

A_0L = ∞

V_i0 = 0

V₂ = (R₁//R₂)I₁

= R₁R₂/(R₁ + R₂)I₁ .....(1)

KCL at inverting node

V₂/R₁ + (V₂ - V₀)/R₂ = 0 (∴ Z_i = ∞)

V₀/R₂ = V₂[1/R₁ + 1/R₂]

V₀/R₂ = (R₁R₂/(R₁ + R₂))I₁[(R₂ + R₁)/R₁R₂]

⇒ V₀ = I₁R₂