A low-power CMOS VGA with 60-dB linearly controlled gain range for GPS application

Abstract

In this paper, a low-power CMOS variable gain amplifier (VGA) with dB-linear gain, which is based on an approximated exponential equation is presented. Being designed for GPS application, the proposed VGA is composed of two cascaded variable gain stages and a fixed gain stage, and has advantages of low-power, wide controlled-gain-range and highly-linear. The VGA is implemented in 0.18 ?m CMOS technology. The simulations show that a total linear gain range of 60 dB (27 dB-87 dB) with 3-dB bandwidth can be obtained at 16 MHz; the IIP3 varies from -11 dBm (at the minimum gain) to -60 dB (at the maximum gain). The power dissipation is less than 2 mA from a 1.8 V supply, and the input referred noise voltage is only 13 ?Vrms (at the 55 dB gain).