ANALOG AND DIGITAL CONVERTING CIRCUIT

PURPOSE:To perform digital conversion by a very small number of comparing means as compared with resolution by using digital outputs obtained from plural cascaded unit quantizing circuits as high-order digit bits successively. CONSTITUTION:An initial-stage unit quantizing circuit ADC1 quantizes an analog input voltage in eight gradations for a full-scale voltage VFS to obtain digital signals D0 - D2 of three bits by conversion, and a trailing-stage unit quantizing circuit ADC2 uses comparison reference potentials right before and after the analog input voltage level among comparison reference potentials generated by a resistance voltage dividing circuit DR1 included in the initial-stage unit quantizing circuit ADC1 as a relative full scale and quantizes the analog input voltage in four gradations to obtain digital signals D3 and D4 of two bits by conversion. The digital signals D3 and D4 constitute low-order digit bits and thus digital conversion to five bits is performed by 12 comparing circuits.