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GATE 2026 IN – Question 45

Analog Electronics · Operational amplifiers and applications · 2 marks · Multiple choice

In the circuit shown below, $R=1\ \mathrm{k}\Omega$ and $R_f=10\ \mathrm{k}\Omega$. If $V_{in}=100\ \mathrm{mV}$ and the op-amps have supply voltages of $\pm15\ \mathrm V$, then $V_{out}$ is ________ V.

Diagram for GATE 2026 IN question 45
  1. −15
  2. 15
  3. 2.1
  4. 1.1

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Show answer and explanation

Correct answer: (C) 2.1

Explanation

Under ideal negative feedback, each inverting input is at the potential of its noninverting input. Thus the voltage across the bridging resistor is $V_{in}$ and its current is $I=V_{in}/R$.

Each feedback resistor contributes $IR_f$ to the output voltage difference, giving $V_{out}=V_{in}+2IR_f=(1+2R_f/R)V_{in}$.

Substituting gives $V_{out}=(1+20)(0.100)=2.1\ \mathrm V$, **C**, using the intended unsaturated operating condition.