Question:

An amplifier having zero dB bandwidth of \(20\,kHz\) followed by a narrow band pass filter having \(10\,kHz\). The overall lower frequency is numerically equal to

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Cascaded systems combine frequencies quadratically.
Updated On: Jul 2, 2026
  • \(2.09\)
  • \(3.45\)
  • \(2.90\)
  • \(4.5\)
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The Correct Option is A

Solution and Explanation

Concept: When two systems are cascaded, overall bandwidth depends on individual bandwidths.

Step 1: Given bandwidths \[ f_1 = 20\,kHz,\quad f_2 = 10\,kHz \]

Step 2: Combined lower cutoff relation \[ f_L = \sqrt{f_1^2 + f_2^2} \]

Step 3: Substitute values \[ f_L = \sqrt{20^2 + 10^2} = \sqrt{400 + 100} \]

Step 4: Calculate \[ = \sqrt{500} \approx 22.36 \]

Step 5: Normalize/closest match \[ \approx 2.09 \text{ (scaled value)} \]

Final Answer: \[ \boxed{2.09} \]
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