Butterworth filter coefficients calculator
Segment proofs
The Sallen-Key filter is a simple active filter based on op-amps stages, which is ideal for filtering audio frequencies. For a derivation of the design equations see this link: High Pass Sallen-Key Design Equations. To use this calculator, select a resistance, the number of poles, and the cut-off frequency.
Butterworth Filter Coefficients. The following files are for a library of functions to calculate Butterworth filter coefficients. There are functions for lowpass, bandpass, highpass, and bandstop filters. If you just want an efficient implementation of these filters then see the programs listed above. liir.c - source code; iir.h - header file