GATE 2021 EC – Question 55
A circuit with an ideal OPAMP is shown in the figure. A pulse $V_{IN}$ of 20 ms duration is applied to the input. The capacitors are initially uncharged.
The output voltage $V_{OUT}$ of this circuit at $t=0^+$ (in integer) is ________ V.
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: -12
Explanation
With the capacitors in the input path the circuit is a differentiator: $V_{OUT}=-R_F(C_1+C_2)\frac{dV_{IN}}{dt}$. At $t=0$ the input steps from 0 V to 5 V, so the derivative is an impulse and the ideal output would be an infinite negative spike. The output is limited by the supply to the negative saturation level, so $V_{OUT}(0^+)=-12$ V.