Patent ID: 7463177

Claim:
A method of designing a digital-to-analog (D/A) converter connected to a voltage generator using voltage drops in a resistor string to generate a plurality of reference voltages forming a monotonic sequence of voltage levels, the D/A converter being one of X D/A converters identically connected in parallel to the voltage generator to generate X analog voltages simultaneously, X being a positive integer, the reference voltages having a variation tolerance of Y percent, Y being a positive number, the resistors in the resistor string having equal resistance values RA, the method comprising: designing a first control circuit for selecting a first arbitrary one of the plurality of reference voltages as a first output, the first control circuit having a series resistance RB when conducting current from the voltage generator to the first output; designing a second control circuit for selecting a second one of the plurality of reference voltages, adjacent in the monotonic sequence to the first one of the plurality of reference voltages, as a second output; and designing a third control circuit for generating a third output from the first output and the second output by turning one or both of a first switching device and a second switching device on, the first switching device being connected in series with a first resistor between the first output and the third output, the second switching device being connected in series with a second resistor between the second output and the third output, the first resistor having a resistance RC such that the combined series resistance of the first resistor and the first control circuit when conducting current is at least (50/Y)·X·RA.