At present,the architecture of a digital-to-analog converter(DAC) in essence is based on the weight current,and the average value of its D/A signal current increases in geometric series according to its digital signal bits increase,which is 2~(n-1) times of its least weight current.But for a dual weight resistance chain type DAC,by using the weight voltage manner to D/A conversion,the D/A signal current is fixed to chain current I_(cha);it is only 1/2~(n-1) order of magnitude of the average signal current value of the weight current type DAC.Its principle is:n pairs dual weight resistances form a resistance chain,which ensures the constancy of the chain current;if digital signals control the total weight resistance from the output point to the zero potential point,that could directly control the total weight voltage of the output point,so that the digital signals directly turn into a sum of the weight voltage signals;thus the following goals are realized:(1) the total current is less than 200μA;(2) the total power consumption is less than 2 m W;(3) an 18-bit conversion can be realized by adopting a multi-grade structure;(4) the chip area is one order of magnitude smaller than the subsection current-steering type DAC;(5) the error depends only on the error of the unit resistance,so it is smaller than the error of the subsection current-steering type DAC; (6) the conversion time is only one action time of switch on or off,so its speed is not lower than the present DAC. At present, the architecture of a digital-to-analog converter (DAC) in essence is based on the weight current, and the average value of its D / A signal current increases in geometric series according to its digital signal bits increase, which is 2 to (n-1) times of its least weight current. For a dual weight resistance chain type DAC, by using the weight voltage manner to D / A conversion, the D / A signal current is fixed to the chain current I_ (cha it is only 1/2 ~ (n-1) order of magnitude of the average signal current value of the weight current type DAC.Its principle is: n pairs of dual weight resistances form a resistance chain, which ensures the constancy of the chain current; if digital signals control the total weight resistance from the output point to the zero potential point, that could directly control the total weight voltage of the output point, so that the digital signals directly turn into a sum of the weight voltage signals; Thus the following goals are realized: (1) the total current is less t han 200 μA; (2) the total power consumption is less than 2 mW; (3) an 18-bit conversion can be realized by adopting a multi-grade structure; (4) the chip area is one order of magnitude smaller than the subsection current-steering type DAC; (5) the error depends only on the error of the unit resistance, so it is smaller than the error of the subsection current-steering type DAC; (6) the conversion time is only one action time of switch on or off, so its speed is not lower than the present DAC.