A CMOS dB-linear variable amplifier using curvematching

Abstract

A CMOS dB-linear Variable Gain Amplifier (VGA) using Curvematching is presented. The CMOS dB-linear VGA provides a variable gain of 59dB while maintaining −3dB bandwidth greater than 86MHz. Curvematching is proposed to obtain the dB-linear gain control characteristics based on a low-distortion source-degenerated differential amplifier structure. Nonideal effects on dB linearity are analyzed and the methods for improvement are suggested. The VGA is designed in a 0.13μm CMOS technology and the post-simulation results demonstrate the good dB linearity, good property of total harmonic distortion and noise figure.