Calculate the output voltage if R₁ = R₂ = R₃ = 50 Ω, Rf = 1 kΩ, and V₁ = V₂ = V₃ = 50 mV.

Question

Question

This question was previously asked in

LPSC ISRO Technical Assistant Electronics 07 Aug 2016 Official Paper

Answer 1

Given: R1 = R2 = R3 = 50 Ω, Rf = 1 kΩ, and V1 = V2 = V3 = 50 mV

F1 Shubham B 27.3.21 Pallavi D6

Due to virtual ground concept:

V_A = VB = 0 ----(1)

Apply Nodal analysis at Node 'A'

$\frac{V_{A} - V_{1}}{R_{1}} + \frac{V_{A} - V_{2}}{R_{2}} + \frac{V_{A} - V_{3}}{R_{3}} + \frac{V_{A} - V_{O}}{R_{f}} = 0$

$\frac{V_{A} - 50 m V}{50} + \frac{V_{A} - 50 m V}{50} + \frac{V_{A} - 50 m V}{50} + \frac{V_{A} - V_{O}}{1000} = 0$

$\frac{3 V_{A}}{50} + \frac{V_{A}}{1000} - 3 m V = \frac{V_{O}}{1000}$

From equation 1);

$- 3 m V = \frac{V_{O}}{1000}$

V₀ = -3.0 V