A $\pm$ 0.75-V Compact CMOS Class-AB Current-Mode Exponential Variable Gain Amplifier

In this brief, a novel class-AB implementation of a current-mode exponential variable gain amplifier (VGA) is presented. The VGA is based on a novel current amplifier circuit implemented by multicoupled MOS translinear loops operating in strong inversion and saturation. The gain is conveniently configured for performing a pseudo-exponential approximation leading to a very compact design since an extra multiplier is not needed. Moreover the VGA can operate with very low voltage and power efficiency. Measurement results from a fabricated prototype in a 0.5-mum n-well CMOS technology reveal gain control up to 12 dB with errors less than plusmn0.5 dB and power consumption of 375 muW for a supply voltage of plusmn0.75 V.