Floating gate current mirror for gain correction in CMOS translinear circuits

IN CMOS TRANSLINEAR CIRCUITS Reid R. Harrison Computation and Neural Systems Program 139-74, California Institute of Technology, Pasadena, CA 91125 [email protected] ABSTRACT The exponential behavior of MOSFETs in subthreshold operation has recently been exploited to build CMOS translinear circuits such as multipliers and log-domain lters. A major obstacle in developing a practical CMOS implementation is the variation in threshold voltage between devices. In translinear circuits, these voltage o sets manifest themselves as gain errors in the current-mode outputs. We have designed a oating-gate CMOS current mirror that can adapt its gain to compensate for these errors. The adaptation process uses only hot-electron injection, so the high voltages typically associated with tunneling are not needed. A small array of these circuits were fabricated in a standard 1.2 m double-poly CMOS process. We demonstrate gain adaptation and discuss the nonlinearity introduced by the adaptive mirror.