Question

6 similar amplifiers are cascaded, with lower cut-off frequency 100Hz. Bandwidth is B1=10 kHz. What is the higher cut-off frequency of the cascaded network?

(a) 4000 Hz

(b) 1667 Hz

(c) 3642 Hz

(d) 3000 Hz

The question was posed to me by my college director while I was bunking the class.

The question is from Cascaded Amplifier in section General and Feedback Amplifiers of Analog Circuits

Answer 1

Correct answer is (c) 3642 Hz

Easiest explanation: fL1 = 50 Hz

fL = 50/ \(\sqrt{2^{1/6}}-1\) = 142 Hz

B1 = 10kHz

B2 = B1 \(\sqrt{2^{1/N}}-1\) = 3.5 Khz

fH – fL = 3500

fH = 3642 Hz.