Amplifier feedback fraction and critical frequency

Thread Starter

ardtuy

Joined Mar 22, 2018
5
I am unsure about a question stated as:
"An amplifier has an open loop gain of 2000 with an upper corner frequency of 500Hz. Determine the required feedback fraction to give a midband gain of 120 and determine the new corner frequency."
I found β = 1/500Hz = 0.002
Then the closed loop bandwidth of the amplifier by BWcl = BWol(1+βAol(mid)) = 2.5kHz
Then to find the the new feedback fraction I used β = 1/120 = 0.0083
I'm not sure if I should have kept the closed loop bandwidth found before and got 2.5kHz/(1+0.0083(120)) = 2.252kHz for the new corner frequency.
Is this wrong?
 

danadak

Joined Mar 10, 2018
3,611
Remember GBW is a constant in single pole roll off circuits. All
bets are off when amp is two pole or greater. Such as in fast
OpAmps for example.

Regards, Dana.
 
Top