GATE 2024 PH – Question 63
Consider the operational amplifier circuit shown in figure. The output voltage V0 is _____ V (in integer).
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Correct answer: -12
Explanation
This is an **inverting summing amplifier** with inputs of 2 V, 3 V and 5 V applied through resistors of 2 kΩ, 3 kΩ and 5 kΩ, and a feedback resistor $R_f=4$ kΩ.
**Virtual ground.** The inverting input is at 0 V, so the input currents add up and flow through the feedback resistor:
$$I=\frac{2}{2\text{ k}\Omega}+\frac{3}{3\text{ k}\Omega}+\frac{5}{5\text{ k}\Omega}=1+1+1=3\text{ mA}.$$
**Output voltage:**
$$V_0=-R_fI=-4\text{ k}\Omega\times3\text{ mA}=\mathbf{-12\ V}.$$