A CMOS Norton amplifier-based digitally controlled VGA for low-power wireless applications

A CMOS variable-gain amplifier (VGA) for use in the baseband section of integrated wireless receivers is presented. The VGA circuit is based on a new CMOS realization of the Norton transresistance amplifier. The proposed CMOS realization operates from a 3-V supply voltage with rail-to-rail swing and class AB input and output stages. The standby current of the class AB stages employed can be accurately controlled, leading to a low power consumption, nonslew-rate-limited response. The VGA circuit provides a precise process-independent gain control range of 30 dB with 1-dB gain step. The circuit uses current division techniques to provide an area-efficient 6-bit digital offset trimming capability. Experimental results from a test chip fabricated through MOSIS are provided.