Simplified pseudo-N-path cells for z to -z/sup N/ transformed SC active filters

Two switched-capacitor (SC) cells for simple design of bandpass active filters from reference lowpass filters are presented. The pseudo-N-path approach used is based on the z to -z/sup N/ transformation. An elliptic sixth-order symmetric bandpass filter with center frequency of 200 kHz and 0.2 dB in-band ripple within a bandwidth of 2 kHz has been designed. The basic lowpass differential topology has been derived using flowgraph techniques from a C03 to 10 21 degrees passive prototype. Presently such a filter is under integration in a 3- mu m double poly CMOS technology.<
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