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In this paper, a CMOS linear-in-dB variable gain amplifier (VGA) is presented. The VGA consists of exponential control block which includes a current squaring circuit, amplifier block and common mode feedback block. Based on the current squaring block which doubles the gain range, a 47dB (-20dB to 27dB) continuous gain range is achieved with a single-stage structure. Simulation results show that the VGA core consumes 3mA of current from a 1.2V supply and has a 3-dB bandwidth greater than 200MHz. The IIP3 and the input referred noise density are within the ranges of 3 to -17dBm and 5 to 68 nV/sqrt(Hz) respectively.
Date of Conference: 6-9 Dec. 2010