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GATE 2014 EE (EE1) – Question 61

Analog and Digital Electronics · Active filters: single stage, Sallen Key, Butterworth · 2 marks · Multiple choice

For the ideal op-amp circuit shown, which alternative gives correct Bode magnitude and phase plots for V₀(ω)/V_i(ω)?

Diagram for GATE 2014 EE (EE1) question 61
  1. Plots A
  2. Plots B
  3. Plots C
  4. Plots D

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Show answer and explanation

Correct answer: (A) Plots A

Explanation

Ideal negative feedback and zero input current make the op-amp a voltage follower even with feedback resistor RF. Its non-inverting input is the RCnode, so H(s)=1/[1+s(1kΩ)(1µF)]=1/(1+0.001s). The pole is1000rad/s, magnitude slope changes0to−20dB/decade, and phase goes0to−π/2. These are the plots in **A**.