Xilinx, Inc.
Radio frequency DAC with improved linearity using shadow capacitor switching

Abstract:

A DAC current steering circuit includes a first transistor whose: drain is coupled to a first output, source is coupled to a drain of a second transistor at a first node, and gate is coupled to a data input, and a third transistor whose: drain is coupled to a second output, source is coupled to a drain of a fourth transistor at a second node, and gate is coupled to a complement of the data input. The circuit further includes first and second shadow capacitors respectively coupled, via first and second switches, between the first and second nodes and ground, the first and second switches respectively controlled by the complement of the data input, and the data input.