Question

Find the 3-dB frequency given that the gain of RC coupled amplifier is 150, the low frequency voltage gain is 100 and the input frequency is 50Hz.

(a) 50.8 Hz

(b) 55.9 Hz

(c) 60Hz

(d) 100Hz

This question was posed to me in an interview for job.

I'm obligated to ask this question of Low Frequency Response and Miller Effect Capacitance in portion Transistor Frequency Response of Analog Circuits

Answer 1

Right answer is (b) 55.9 Hz

Easiest explanation: AVM = 150

AVL = 100

f = 50Hz

100 = \(\frac{150}{\sqrt{1}}+(\frac{f_L}{50})^2\)

1+f^2/2500 = 1.5^2

f^2 = 2500*1.25 = 3125

f = 55.90 Hz.