This group contains a -3dB/octave filter, plus the classic Bessel, Butterworth, Chebyshev, inverse Chebyshev and Cauer, implementated as active filters with infinite (floating) input and
1Ω output resistance. It's accurate for Butterworth, Chebyshev and InvChebyshev, and for Bessel if used as a time delay (otherwise some minor errors for frequency scaling due to a curve-fitting approximation). There are minor roll-off errors for 3dBoct and Cauer may drop well below
~2~3 decimals precision for extreme settings due to the elliptic functions approximations.
©Vlad, 2008 - 2015