Patent ID: 8836554

Claim:
A digital-to-analog converter circuit comprising: P pieces of conversion cells including A pieces of known weight conversion cells and (P-A) pieces of unknown weight conversion cells; an output switching circuit electrically connecting with P pieces of said conversion cells and receiving output of each said conversion cell, dynamically selecting N pieces of said conversion cells from P pieces of said conversion cells as reference conversion cell groups, which at least include A pieces of said know weight conversion cells, according to digital control signals of a reference group in an error estimation mode, outputting a reference output (Ir) proportionally according to said digital control signals of said reference group, dynamically selecting at least one said unknown weight conversion cell from (P-A) pieces of said unknown weight conversion cells as pre-calibration conversion cell groups according to digital control signals of a pre-calibration group, and generating a pre-calibration output (Ic) smaller than a maximum value of said reference output; an analog-to-digital converter generating a digital pre-calibration signal (Do) according to a difference of said reference output (Ir) and said pre-calibration signal (Ic); a digital controller electrically connecting with said analog-to-digital converter and said output switching circuit, generating said digital control signals of said reference group and said digital control signals of said pre-calibration group to make said reference output approximate said pre-calibration output, generating a digital weight output after receiving said digital calibration signal (Do), using said digital weight outputs to establish a weight table, and working out an actual digital weight of each said unknown weight conversion cell according to said weight table; and a calibration memory electrically connecting with said digital controller and storing said actual digital weight of each said unknown weight conversion cell, which said digital controller works out according to said weight table.