Disclosed are a high-precision successive approximation type analog-digital converter and a DNL-based performance improvement method. The analog-digital converter comprises a redundancy weight capacitor array, a comparator, a coding and reconstructing circuit, a weight storage circuit and a control logic circuit; the redundancy weight capacitor array is used for acquiring an input voltage at a sampling stage to generate an output voltage and for realizing, at a conversion stage, voltage addition and subtraction operations by controlling the corresponding weight capacitors of the redundancy weight capacitor array according to the results output by the comparator; the comparator is used for comparing the output voltages of the redundancy weight capacitor array; the coding and reconstructing circuit is used for calculating an output code of the successive approximation type analog-digital converter according to the results output by the comparator and the capacitor weight in the weight storage circuit; the weight storage circuit is used for storing capacitor weights; and the control logic circuit is used for controlling the sampling and conversion stages of the redundancy weight capacitor array. Due to the use of a capacitor array with redundancy weights in the analog-digital converter, digital correction for capacitor mismatch errors is realized, and both the conversion speed and the degree of linearity are improved.
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