Highpass and bandpass 2nd-order switched-capacitor filters

Highpass and bandpass switched-capacitor filters derived from Sallen and Key, and Bach´s RC active highpass filters have been described. The bandpass filters have been shown to be realisable by simple modification of the highpass filters, using Laker´s method of obtaining 1st-order lowpass filters from 1st-order highpass filters under certain input conditions. A single amplifier version of a recently described bandpass filter has also been discussed. All the realisations have been compared regarding the capacitor spread required to realise desired pole frequency and pole Q for given sampling frequency and optimised for minimal capacitor spread.