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GATE 2022 EE – Question 44

Analog and Digital Electronics · Operational amplifiers: characteristics and applications · 2 marks · Multiple choice

The current gain ($I_{out}/I_{in}$) in the circuit with an ideal current amplifier given below is

Diagram for GATE 2022 EE question 44
  1. $\dfrac{C_f}{C_c}$
  2. $\dfrac{-C_f}{C_c}$
  3. $\dfrac{C_c}{C_f}$
  4. $\dfrac{-C_c}{C_f}$

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Correct answer: (D) $\dfrac{-C_c}{C_f}$

Explanation

The inverting input is a virtual ground, so the input current flows through the feedback capacitor $C_f$ and the output voltage is $V_o=-\frac{I_{in}}{sC_f}$. The output current through $C_c$ into the grounded load is $I_{out}=sC_cV_o=-\frac{C_c}{C_f}I_{in}$, so the gain is $-\frac{C_c}{C_f}$.