Analog-digital converter realizing high integation with high resolution ability

摘要

An analog-digital converter comprises a first comparing-converting device for comparing analog input voltages and a plurality of primary reference voltages at different levels, respectively, and converting the analog input voltages to digital signals on the most significant bit sides; a reference voltage generating device for generating a plurality of secondary reference voltages at different levels from the primary reference voltages supplied to both terminals of the reference voltage generating device; a switching device for supplying the primary reference voltage most close in sequential order to the analog input voltages to the reference voltage generating device in accordance with the compared results of the first comparing-converting device; a second comparing-converting device for converting the compared results between the analog input voltages and the secondary reference voltages to signals corresponding to digital signals on the least significant bit side with respect to the analog input voltages; and a selecting device for selecting signals based on the outputs of the second comparing-converting device in accordance with the potential relation of both input terminals of the reference voltage generating device to provide digital signals on the least significant bit side with respect to the analog input voltages.