A CMOS Digitally Controlled RF Variable Gain Amplifier

A new digitally controlled decibel-linear variable gain amplifier (VGA) is presented. The proposed VGA uses a folded cascode opamp and a capacitance-selecting technique to provide dB-linear gain control. The VGA provides a 36.6dB gain control range with a gain error less than 0.2dB while operating at 1GHz. It can also be operated at 2GHz to give a 28dB gain control range with an error less than 0.65dB. The power consumption is 10.77mW at 1.8V supply voltage