Feasible designs for high order switched-current filters

Abstract

Fully-balanced integrators based on S/sup 2/I type memory cells are introduced for realising bilinear-LDI switched-current ladder filters. The problems of high component spreads and large silicon area encountered in very high order designs are overcome by adopting modified approximation and prototype ladder manipulation techniques, resulting in a typical example of a 21st order elliptic lowpass filter with a spread of 13.63. Modifications that allow for simplified input stages are also presented.