A low-power digitally-programmable accurate decibel-linear CMOS VGA for UWB systems

Abstract

A new current-mode circuit for realizing CMOS digitally controlled decibel-linear variable gain amplifier (VGA) is proposed for ultra-wideband systems. The core block of this VGA is a series of programmable current-amplifier cells which are connected by a switch array. Some cells can be cut off under certain gain modes to save the power. Designed in 0.18..m CMOS technology, the VGA provides a 45d B gain range (from 7 dB to 52 dB) with 3 dB per step and a gain error of less than 0.1 dB, and its minimal bandwidth is 285 MHz with a load capacitor of 0.5 pF. The VGA consumes only 6.6-mW on average (from 4.85-8.35 mW), and the range of IIP3 is from -11 dBm to -40 dBm.