| xitronics |
I intend to design a 4th order Butterworth MFB low pass filter with 20khz cutoff.
I want to include a pot for varying the phase response for the cut-off frequency marginally (+- 15deg). Which passive component should I keep variable so as to have minimal impact on the gain & cutoff frequency..?
I have posted the schematic for direct reference.
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Regards,
Xitronics. |
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| jcx |
in a minimum phase system amplitude and phase are codeterminant - specify one and the other is completely determined
So you can't change phase and have Butterworth response by changing any component of the filter
you can add a series all-pass circuit that is non-minmum phase and can adjust the phase shift without changing the amplitude response |
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