The two stage of a cascade amplifier have individual upper

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The two stage of a cascade amplifier have individual upper cut off frequencies at f₁ = 5 MHz and f₂ = 3.33 MHz. The best approximation for the upper cut-off of the cascade is:

1. 4.16 MHz
2. 3.33 MHz
3. 2.00 MHz
4. 5.00 MHz

Correct Option: C

Upper cut-off frequency of first stage f₁ = 5 MHz
upper cut-off frequency of II^nd stage f₂ = 3.33 MHz after cascading
f₁* = f₁ √2^1/n= 1 = √2^1/2 - 1
= √0·414 = 3.217 MHz

after cascading f₂* =	f₂	=	3·33
	√2^1/n - 1		√1·414 – 1

= 5.17 MHz
n = 2 (for two cascaded stage) upper cut-off after cascading the two stages
= 5.17 – 3.217
= 1.905 MHz ≈ 2 MHz