A CMOS Variable Gain Amplifier with DC Offset Calibration Loop for Wireless Communications

Abstract

A 64 dB gain range VGA with DC offset calibration loop is proposed in this work. This VGA adopts the degeneration type amplifier to vary voltage gain and uses the super-source-follower input stage to enhance the linearity. A digital-based DC offset calibration loop is also designed to solve the DC offset problem. An experimental chip is fabricated in 0.18 mum process. With 2 dB step, the gain error is less than 0.8 dB and the output DC offset is less than 100mV at maximum gain setting. The total power consumption is 11 mW