Filter categories FIR and IIR

FIR filter

The FIR filters are non-recursive notch filters. A notch filter has zeros (notches) in its frequency response at the filter frequency and multiples of the filter frequency. These frequencies are therefore attenuated in amplitude.

Example of a typical attenuation curve of a notch filter with 50 Hz filter frequency:

IIR filter

The IIR filters are low-pass filters.

IIR1 has the highest cut-off frequency, IIR8 has the lowest cut-off frequency.