A CMOS wideband linear-in-dB VGA for UWB applications

Abstract

A CMOS wideband variable gain amplifier (VGA) with an exponential gain control characteristic is presented. The exponential gain control function is realized by changing the tail currents a differential gain stage. The bandwidth is extended by using an inductive peaking technique. The gain (in dB) of the VGA is varied linearly from -41 dB to 31 dB with respect to a control voltage from 1.38 V to 1.1 V. The bandwidth of the proposed VGA is larger than 1 GHz with a gain control range of 72 dB. A DC offset cancellation loop is included so as to avoid amplification of the DC offset. The VGA is powered by 1. 8 V with 13.5 mA. The VGA chip occupies an area of 220 mu m X 620 mu m. (c) 2007 Wiley Periodicals, Inc.