Topic: Analog Circuits
Consider a single stage tuned amplifier having 3dB bandwidth of 100 kHz. Determine the bandwidth if two such single stage tuned amplifiers are cascaded.
- A. 1000 kHz
- B. 10 kHz
- C. 41.4 kHz
- D. 64.3 kHz
Answer: D. 64.3 kHz
Explanation: When $n$ identical single-stage tuned amplifiers are cascaded, the overall bandwidth is given by $BW_{overall} = BW_{single} \times \sqrt{2^{1/n}-1}$.
For $n=2$, $BW_{overall} = 100\text{ kHz} \times \sqrt{2^{1/2}-1} = 100 \times \sqrt{1.414-1} = 100 \times \sqrt{0.414} \approx 100 \times 0.643 = 64.3\text{ kHz}$.