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Signal Chain filtering - Filter pole sensitivity

How do you find pole sensitivity of the filter?

  • The pole sensitivity of a filter circuit depends on the Q value of a complex pole pair. Increasing the Q value of a second order filter increases the frequency response amplitude peaking and phase rate of change near the minus 3dB frequency (fc). In addition, the transient response overshoot and settling time increase with increasing Q. Pole sensitivity can be calculated or intuitively understood by using frequency and time response of a second order lowpass filter. Q values of 1, 2, and 5 plots illustrate the effect of increasing Q. In active RC filters increasing the Q value of a complex pole increases the GBW requirement of an op amp and the precision of passive components. For Q values higher than five (typically for a bandpass filter), the pole sensitivity increases substantially.