Designing On-Chip Active RC Filters for the Analog Front End (AFE)

Abstract

Summary form only given. Since the early days of microminiaturization in the 1970's and 70's, the design and implementation of filters has presented a special problem. The reason for this is mainly that conventional LCR filters, and in particular, inductors, cannot be miniaturized, let alone integrated, on a chip. Thus, for the last forty years or so, inductorless alternatives to LCR filters that are compatible with microminiaturization and on-chip integration have been developed. This continues to be necessary because, in spite of the 'digital revolution', the so-called 'analog front end' (AFE) of most electronic devices, which interface with the real world, is and will continue to be, analog. In this talk, a brief historical overview of the many attempts at finding inductorless filters is first given. The overview ranges from hybrid integrated thin and thick film circuits of the 60's and 70's, to switched capacitor and switched current filters of the 80's and 90's, and on to the present day continuous time active RC filters that are amenable to mixed mode on-chip implementation. Some of the main present day methods of designing active RC filters for on-chip design are covered. These methods cover signal flow graph simulation of LC ladder filters, multiamplifier biquads, ladder-biquad combinations, and the design of frequency-dependent capacitors and inductors. Examples from the area of high speed wire-bound digital data communication systems (ADSL and VDSL) are given