[sdiy] DC 'bounce' in second order filters

Harry Bissell harrybissell at wowway.com
Wed Nov 23 15:06:16 CET 2011


OK let's try this

I have a second order VCF  When I first apply a signal to it (starting from a zero condition) the filter
have a DC bounce (of one polarity or another) which prevents the signal output from crossing zero for a couple of cycles.

The overall shape of the bounce looks critically damped, it overshoots in one polarity then recovers in the other polarity before becoming
DC stable. The filter is not resonant (Q=.707 or so I believe)

Is the bounce an unavoidable artifact of a second (or higher) order filter, or can I do anything to reduce it. In my application missing a zero
cross is an error condition I'd like to avoid

your thoughts ???

H^) harry



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