MOS-only M-2M DAC for ultra-low voltage applications

This work presents a study of the CMOS based R-2R ladder network (also called M-2M) Digital-to-Analog Converter (DAC) as a potential candidate for ultra-low voltage (ULV) applications, i.e. supply voltages VDD lower than 200mV. MOS transistors operate in subthreshold under such very low VDD, and the circuit analysis must be done using an all-region continuous MOSFET model. Simulation results in a commercial 130 nm process corroborate the presented analysis, showing that it is possible to implement this DAC topology for 6 to 8 bits operating under supply voltages from 70 mV to 140 mV.