Digital-to-analog converter and analog-to-digital converter with controllable bi-polar and uni-polar capability

Claim 1

A uni-polar/bi-polar digital-to-analog converter comprising digital-to-analog converter means having first and second current bus outputs, first and second current-to-voltage converters coupled to said first and second current bus outputs respectively, switching means coupling the output of said second current-to-voltage converter to the input of said first current-to-voltage converter, said switching means comprising a field effect transistor switch, said second current-to-voltage converter comprising an operational amplifier and a feed-back path connecting the output of said operational amplifier to its input, said feed-back path including a continuously conducting field effect transistor matched in resistance to said field effect transistor switch over the operating temperature range of said uni-polar/bi-polar digital-to-analog converter, said field effect transistor switch and said field effect transistor comprises a dual integrated FET with matched channel characteristics, and control means for selecting uni-polar or bi-polar operation, said control means controlling the conductivity of said field effect transistor switch in accordance with the selection of uni-polar or bi-polar operation.