Abundance of ladder digital to analog converters

A general digital to analog converter (DAC), which encompasses popularly known weighted resistor and R-2R ladder DACs as the special cases, is introduced. The weighted resistor sub-family has been studied in the recent past. This paper presents a detailed study of the sub-family of ladder DACs. Some DACs have one or more interesting features, such as, minimum number of resistors, minimum spread, minimum total resistance, all equal-valued resistors. It is interesting to note that the R-2R ladder DAC when realized with all equal valued resistors not only has the least possible spread but also has the minimum total resistance. Also there is another DAC which has the same spread of 2 as R-2R ladder DAC but requires the minimum number of resistors.