A scalable high-performance switched-capacitor filter

Switched-capacitor filters tend to display reduced performance when implemented at reduced feature size because of higher KT/C and 1/f noise, and reduced operational amplifier gain and swing. Descriptions are given of circuit solutions to certain performance degradations associated with technology scaling, including chopper stabilization, and class AB differential operational amplifier architecture. An experimental fifth-order elliptic PCM low-pass filter, using 3-μm CMOS technology, achieved an area of 200 mil per pole. Typical measured results for a ±2.5-V power supply are a dynamic range of 87 dB and a power supply rejection ratio of 40 dB over 1-MHz range.