Guest 4electros Posted March 27, 2006 Report Share Posted March 27, 2006 I was wondering about the disadvantages of the simple filters consisting of resistors and capacitors and use active filters instead of it?what are the advantages of active filters over simple filters that make us use it?what about using inductors for such purposes , i found that is omitted from such purposes, could anyone explain why?!regards Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted April 8, 2006 Report Share Posted April 8, 2006 Try using a passive filter at a high frequency. It doesn't do much. 20db per decade. Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 8, 2006 Report Share Posted April 8, 2006 Each stage of an LC passive filter provides a drop of 40dB per decade. An RL or RC passive filter is only 20dB per decade.I use active filters with a sharp-cutoff Butterworth response for most audio filters.I have used switched-capacitor lowpass and bandpass filter ICs to make extremely low distortion oscillators and a distortion analyser.You can feed a square-wave into a multiple stage switched-capacitor lowpass filter IC and get a perfect sinewave output. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted April 8, 2006 Report Share Posted April 8, 2006 I think most designs should go for chebychev until it becomes a nuisance. Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 8, 2006 Report Share Posted April 8, 2006 I think most designs should go for chebychev until it becomes a nuisance.A chebychev filter has ripple in its passband and has extrene phase fluctuations.A Butterworth filter has an absolutely flat frequency response then a sharp cutoff. Its phase response is reasonable.A Bessel filter has a droopy frequency response and the least amount of phase shift. Quote Link to comment Share on other sites More sharing options...
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