An Overview of CMOS Variable Gain Amplifiers

Variable gain amplifier(VGA) is an analog circuit,which varies gain,adjusts signal dynamic range and stabilizes signal power.An overview of CMOS integrated variable gain amplifiers is made.The definition of VGA and its function,classification and specifications are elaborated.Different openand closed-loop VGA's are described,and the advantages and disadvantages of gain control strategies are analyzed.Approaches to achieving exponential gain in CMOS technology are explained.Finally,examples of high performance VGA's used in wireless digital communication are introduced,which mainly focus on broad bandwidth,high linearity and low supply power.