| 摘要 |
PROBLEM TO BE SOLVED: To improve the linearity of D/A conversion characteristic and to improve the precision of low-order bits of A/D converted data by using a PWM type D/A converting device as a D/A converter in an A/D converting device which obtains A/D converted data of resolution higher than the resolution of an A/D converter by converting from analog to digital the voltage obtained by amplifying the difference voltage between the voltage obtained by converting the A/D converted data of an input voltage from digital to analog and an input voltage and putting the two pieces of A/D converted data together. SOLUTION: A PWM circuit part 7 generates an outputs a PWM signal 7a with a duty factor corresponding to A/D converted data of a sample-and-hold voltage VA. The PWM signal 7a is smoothed by a low-pass filter circuit 5 to obtain an analog voltage VD. Differential amplifiers 3 and 4 output the voltage generated by raising to n-th power the difference voltage between the sample-and-hold voltage and analog voltage. A control part 8 puts together the A/D converted data as the amplification output of the difference voltage and the A/D converted data of the sample-and-hold voltage to obtain A/D converted data of resolution which is n-bit higher than the resolution of the A/D converter.
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