Whenever I was choosing values for filters I always ignored the phase angle plots, but should I be taking it into consideration when for example designing a high-pass filter for the input of an amplifier or a low-pass filter in the feedback network? What are the situations where it's important to know the phase angle and take it into consideration in the design?
Electronic – Is phase angle a important thing to consider when designing filters
filterphase shift
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Best Answer
From system theory we know that the negative slope of the phase response gives the so called "group delay" of the filter. For some applications - e.g. filtering of squarewave signals - we want to have a group delay as constant as possible (identical to a linear phase response) in order to retain the original waveform (in spite of filtering).
This requirement was the reason to define the Thomson/Bessel response as one of the standard filter functions. As an another example: We have allpass filters (constant magnitude over frequency) with the only purpose to shape/correct the phase response (resp. group delay) of other filter ciruits (Delay equalizer).