A high performance CMOS compatible 8-bit current scaling D/A convertor

An 8-bit current scaling D/A convertor has been implemented in a standard 3 μm p-well CMOS process. This convertor requires an active area of 1 mm² and is capable of operating at full scale currents ranging from 50 nA to 1 mA. High linearity at low full-scale (FS) currents is achieved by using CMOS compatible lateral bipolar transistors rather than MOS transistors or precision resistors to create the weighted currents. High switching speed is obtained at low current levels through improved current switch design. Test results show that differential nonlinearity is typically ±0.1% FS, integral nonlinearity is ±0.07% FS and the settling time is 35 ns. Two complementary output currents with high output impedance and high voltage compliance are provided