"SALLEN KEY" ACTIVE FILTER DESIGNING

[Audioguru]

But a Chebychev filter has ripple in its passband frequencies. A "Butterworth" filter with too much gain has an absolutely flat passband.

 

[keith1200rs]

A Chebyshev with only two poles will only have one peak, not "ripple". You need at least 4 poles to see ripple. If a filter is not maximally flat it is not a Butterworth. A Butterworth with "too much gain" is not a Butterworth.

Keith.

 

[Audioguru]

My "Butterworth' filter with too much gain is actually a Bessel filter with too much gain.

 

[keith1200rs]

My "Butterworth' filter with too much gain is actually a Bessel filter with too much gain.

I don't think this is a helpful or correct way to describe filters. It is a bit like saying a Legendre filter is really a Chebyshev if I change the component values.

A Bessel is a Bessel. A Butterworth is a Butterworth. If you deviate from the characteristics of the filters by changing the values then it is NOT the named filter anymore.

Keith.

 

[LvW]

I only can agree with KEITH - especially with his 17:11 contribution.