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What is the Roll-Off frequency of this op-amp integrator?

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dr.power

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Hello there buddies...

I have just 2 simple questions regarding the below op-amp circuit which is a double integrator (low pass filter) and takes the integral of the input signal (The input audio signal is between 20Hz to 5kHz).
1. What is the roll off frequency of each stage of this circuit in dB/Octave?
2. What is the roll off frequency of the whole circuit (from the input to the output) in dB per Octave?

Thank you so much
 

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MikeMl

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Detailed answer depends on the values of the R's and C's, and to a lesser extent on the GBW of the opamps.

for example: the cutoff freq of the right-hand stage is higher than the left one:

391.png

Both have unity gain below their respective cutoff...

Ultimate roll-off is 40db/decade

-40db/decade is easily attainable with a single op-amp stage as a 2pole Butterworth LPF:

391b.png
 
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