Low-Power CMOS Variable Gain Amplifier with Wide Gain Range and dB-Linear Characteristic

Abstract

This paper proposes a structure for an all-CMOS variable gain amplifier (VGA) which provides very wide gain range, small chip size and low power consumption. An exponential approximation function with a very wide decibel linear control range was utilized. The VGA is composed of two cascaded variable gain stages, a control stage and a current generator. The VGA has the maximum gain variation of 110 dB with a linearity error of less than ± 1 dB, 3-dB bandwidth of 10 MHz ~ 1.67 GHz and power consumption of 3.7 mW from a 1.2-V supply. This VGA topology that can provide a very wide gain variation and reduce power dissipation while occupying smaller chip size and featuring high linearity will be very useful in many applications.