Let's say I have a 2nd order low-pass filter in a Sallen-Key configuration (Chebyshev), and the cutoff frequency should be the frequency at which the phase shift becomes -90°, how will the GBW (gain bandwidth product) of the op-amp I choose affect the position of the cut-off frequency?
Will choosing an op-amp with a higher GBW shift the cut-off frequency higher?
This was my problem during my laboratory session. I built a 3rd order low pass (Chebyshev, Sallen-key) filter using the filter design tool from TI. During the lab I changed the op-amps with two TL081s, and I had to connect the input signal to the 2nd stage and measure its cutoff frequency. I got a much higher cutoff frequency from the design tool report by about 10x.
Answer : if anyone wants a detailed answer you can find it in this book there is a section called Dynamic Op Amp Limitations-EFFECT OF FINITE GBP ON FILTERS.
Sergio Franco - Design With Operational Amplifiers And Analog Integrated Circuits-McGraw-Hill Series in Electrical and Computer Engineering