GATE 2023 IN – Question 60
The ideal switched-opamp circuit has $V_{in}=100$ mV. At $t=0$, the 10 nF capacitor stores 1 nC with the shown polarity. A 1 kHz square wave $V_s$ controls the switch: HIGH selects position 1; LOW selects position 2. At $t=20$ ms, the magnitude of $V_o$ is ______ mV (nearest integer).
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Correct answer: 99 to 101
Explanation
Initial feedback charge gives $V_o=+(1\ \mathrm{nC})/(10\ \mathrm{nF})=100$ mV. Each cycle transfers $(1\ \mathrm{nF})(100\ \mathrm{mV})=0.1$ nC to the virtual-ground node, lowering output by 10 mV. Twenty cycles lower it by 200 mV to −100 mV. Requested magnitude: **100 mV**.