CURRENT FEEDBACK OP-AMP UTILIZES NEW CURRENT CELL TO ENHANCE THE CMRR

Abstract

Despite excellent high frequency and high speed performance, current-feedback operational amplifiers (CFOAs) generally exhibit poor common-mode rejection (CMRR) properties, which limit their utility [Analogue IC design: The current–mode approach, IEE Circuits and Systems Series, Peter peregrinus, 1990]. A novel current feedback operational amplifier (CFOA) with improved performance is presented. The proposed CFOA has a new current-cell [Novel current-feedback operational amplifier Design Based on a floating circuit technique, IEE Colloquium on Analogue Signal Processing, 1998], to bias the entire circuit, which achieves an incremental output resistance twice that of the well-known "Wilson" circuit. Simulation results of this new CFOA architecture indicate that the amplifier exhibits performance characteristics superior to those obtained with an established input architecture: in particular, the CMRR (common-mode rejection ratio) is 91 dB, and the d.c. offset voltage less than 26 μV.