Ultra low-voltage, low-power, and high dB-linear variable gain amplifier

Abstract

Low-voltage low-power VLSI circuits are of particular interest in the field of microelectronics. The demands for low-voltage systems are driven by the factors of technology, design, and market. The variable gain amplifier (VGA) is an indispensable function block for wireless communication systems. This VGA is not used for telecommunication applications, but also for many other applications; such as hearing aids, disk drive, ... etc. In this paper, an ultra low-voltage, low-power, and high dB-linear VGA and an all CMOS exponential V-I converter are proposed. The proposed V-I converter is based on the Taylor series expansion for realizing the exponential characteristics. The techniques to increase the dB-linear output current range of the V-I converter are introduced, and this converter is used to control the gain of the VGA. The proposed VGA has advantages over previous works that it can operate at extreme low-power and low-voltage applications, and achieves a high control gain range. Based on a 0.25$\mum$ CMOS process, the proposed VGA achieves more than 40 dB of control gain range with the linearity error less than $\pm$0.5dB. The total power consumption is less than 1.5mW at 1.25 V supply voltage.