1.5-V Square-Root Domain Second-Order Filter With On-Chip Tuning

摘要

A novel square-root domain (SRD) second order filter with automatic tuning control is described. The tuning system is based on a master-slave configuration, where the master is a SRD current-mode magnitude locked loop. The control circuitry allows tuning of the cut-off frequency as well as the quality factor and gain of the filter. The basic building blocks of the complete system are implemented employing a design strategy based on the inherent nonlinear characteristic of Class-AB linear transconductors. A proper biasing scheme in such transconduc-tors leads to operation with very low supply voltages (as low as V{sub}(GS) + 2V{sub}(DSsat)). Simulation and numerical results together with measurements from a fabricated prototype in a 0.8-μm CMOS technology are included in order to validate the design technique proposed.