High dynamic range variable-gain amplifier for CDMA wireless applications

A variable-gain amplifier (VGA) integrated in an 0.8 /spl mu/m 12 GHz process, has input dynamic range of 90 dB with 5 dB noise figure at 45 dB of gain and -3 dBm IIP3 at -45 dB gain. The chip occupies 1 mm/sup 2/, uses a single 3.6 V supply, achieves at least 250 MHz bandwidth, and has excellent performance over temperature. In CDMA transceivers, VGAs are needed for both the receiver and transmitter automatic gain control. A transmit VGA is needed in CDMA systems to regulate each mobile unit transmit power so equal power from each user is received at the base station to optimize system capacity. The realization of the receiver VGA is in a BiCMOS process that has n-p-n transistors with f/sub t/=12 GHz and MOS transistors with an L/sub eff/=0.8 /spl mu/m. Concepts developed for the receiver VGA circuit are also used to design the transmitter VGA.