An 80-dB linear baseband CMOS VGA with temperature compensation for low-power application

In this paper, a low-power CMOS variable gain amplifier (VGA) with an approximated exponential equation is presented. 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 temperature independent. The VGA is implemented in 0.18 um CMOS technology. The simulations show that a total linear gain range of 80 dB (-15 dB~65 dB) with 3-dB bandwidth can be obtained at 50 MHz; the IIP3 varies from -4 dBm to -40 dBm. The power dissipation is less than 2.2 mA from a 1.8 V supply voltage; the NF is only 14 dB (at the 65 dB gain). And the control circuit provides a gain error lower than ±1.5 dB over the full temperature and gain ranges.