Question about an op-amp that has three internal amplifier stages....

Question

a certain op-amp has three internal amplifier stages with midrange gains of 30 dB, 40 dB, and 20 dB. Each stage also has a critical frequency associated with it as follows: Fc1 = 600 Hz, Fc2 = 50 kHz, and Fc3 = 200 kHz....

a) what is the midrange open-loop gain of the op-amp expressed in dB?

b) What's the total phase shift through the amplifier, including inverstion, when the signal frequency is 10 kHz?

alright I got a) 53 dB and i cant figure out B and i kno my A is wrong..can someone help?

Answer 1

the midrange gain is just the sum of the 3, 90dB. But that depends on how you define "mid range"!  I define it as DC to 500 Hz.

At 10kHz, only one of the poles is effective, so the phase shift is 90 degrees. "including inversion" doesn't mean too much. From the - input there is a 180 phase shift, from the + none. add to that the 90 shift from the pole.

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