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GATE 2015 EE (EE2) – Question 24

Analog and Digital Electronics · Active filters: single stage, Sallen Key, Butterworth · 1 mark · Multiple choice

Filters F1 and F2 have the shown low-pass and high-pass characteristics and are combined as shown. Their cutoffs satisfy f1<f2. The result behaves as a

Diagram for GATE 2015 EE (EE2) question 24
  1. band-pass filter
  2. band-stop filter
  3. all-pass filter
  4. high-Q filter

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Show answer and explanation

Correct answer: (B) band-stop filter

Explanation

F1 passes frequencies below f1 and F2 passes frequencies above f2. The equal input resistors combine their outputs at the ideal op-amp's noninverting input, while the output feeds the inverting input.

Low frequencies pass through F1, and high frequencies pass through F2. In the intermediate band f1<f<f2 both branches are attenuated. The combined response therefore has a rejected middle band: **band-stop, B**.

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