A 4.5-7.5 GHz CMOS Variable Gain Amplifier with Low Errors for Receiver Channels

a two-stage programmable CMOS variable-gain-amplifier (VGA) was presented. It consists of a passive stage, an active stage and an inter-stage matching transformer. The gain tuning of each stage VGA can be digitally-controlled, and 32/24 gain states are obtained for the passive /active stage. As a result, 768 states in total can be get for the two-stage VGA. The proposed VGA was implemented in a 180-nm CMOS process and integrated into a receiver channel. Then a digital program was used to select the desired gain states from the total 768 measured states of the chip, to realize a highly accurate gain tuning. And an ultra-low root-mean-square (rms) phase/gain error less than 1.88 degrees/0.19 dB of rms phase/ gain error was obtained over 4.5 to 7.5 GHz band.