Analog NMOS sampled-data recursive filter

MONOLITHIC INTEGRATION of precision audio frequency filters has been a difficult objective to reach. Active RC filters using numerous off-chip precision RC elements have been in use for years’. Transversal filters using CCD or BBD approaches occupy very large silicon areas when fully integrated with all peripheral circuits2. Fully integrated digital filters require precision linear A/D coders and also require a large silicon area . Analog sampled data recursive filters have been described previously, but these employed many off-chip precision components.