Low-Voltage CMOS Nonlinear Transconductors and Their Application to Companding Current-Mode Filters

摘要

Two novel nonlinear CMOS transconductors that can be employed for building CMOS current-mode filters are presented and their performances compared to formerly proposed topologies aimed at the same goal. The first one is based on a previous topology proposed by the authors, where a new biasing procedure leads to an improved performance for low supply voltages. The second one follows a novel approach, based on cascading a transresistor and a transconductor. The analysis is complemented with a more general approach based on the identification of translinear loops present in the circuit. Both nonlinear transconductors can operate at supply voltages as low as one V{sub}(GS) plus two V{sub}(DS) of a saturated MOSFET. CMOS current-mode filters based on these blocks are built following companding techniques, and their correct operation is validated by simulation and experimental results.