An area-efficient coarse-fine resistor-string D/A converter

This paper proposes an area-efficient coarse-fine resistor-string digital-to-analog converter (DAC). It reduces the number of the unit resistors and switches in the resistor-string DAC by dividing the resistor-string into coarse and fine resistor-strings. It makes the analog output by summing two voltages generated in the coarse and fine resistor-strings. A bias current flows through the series-connected coarse and fine resistor-strings. The number of the unit resistors in the proposed 12-bit DAC is reduced to 12% and 77% of the conventional resistor-string DAC and inverted-ladder DAC [1]. The simulations and implementations are performed in a 0.18μm CMOS process with VDD=1.8V.