Jin-Sub Choi

Highly linear variable gain amplifiers with programmable temperature compensation for CDMA wireless applications

Highly linear and low power variable gain amplifiers (VGAs) with digitally programmable temperature compensation has been developed using a 15 GHz 0.5 /spl mu/m BiCMOS process for CDMA mobile phones. Receive-VGA (RxVGA) shows 135-dB gain control range, 4.95 dB noise figure at a maximum gain, and -1.35 dBm IIP3 at a minimum gain with current consumption of 8 mA. Transmit-VGA (TxVGA) shows an output P/sub 1 dB/ of 4.7 dBm with current consumption varying from 6 mA to 24 mA according to its gain. The temperature compensation has been achieved within /spl plusmn/0.2 dB variation over the entire temperature and gain range. In addition, for easy application of the VGAs for mobile handsets, a simple method is presented for a programmable temperature compensation. A two-bit digital input is used to modify the temperature compensation characteristics by 1.5 dB/1110/spl deg/C per a step.