GATE 2020 EC – Question 51
The components in the circuit given below are ideal. If $R=2\ \text{k}\Omega$ and $C=1\ \mu$F, the $-3$ dB cut-off frequency of the circuit in Hz is
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Correct answer: (D) 79.58
Explanation
The shunt branch ($2C\,\|\,2R$) connects to the inverting input, which is a virtual ground, so it has no effect. The gain is $-\frac{R\|\frac{1}{j\omega C}}{R}=-\frac{1}{1+j\omega RC}$. The $-3$ dB frequency is $f_c=\frac{1}{2\pi RC}=\frac{1}{2\pi\times2\times10^3\times10^{-6}}=79.58$ Hz.