PURPOSE: To attain the high speed of the operation of an A/D converter by unnecessitating the amplifier circuit of a high gain causing a speed decrease, and narrowing a voltage swing width.
CONSTITUTION: An analog input voltage from an input terminal 1 is converted into a digital code by an A/D converting means 6, stored in an AGC 9, and converted into the analog voltage again by a D/A converting means 7. Then, a difference between the analog voltage and the analog input voltage is searched, amplified by an amplifier circuit 8, supplied to the A/D converting means 6 as the new analog input voltage, converted into the digital code again, and integrated with the previously searched digital code so that the digital code is obtained. An amplifier circuit 4 which multiplies the analog input voltage by 1/n is provided at the input side of the A/D converting means 6, and the full scale input voltage of the A/D converting means 6 is made 1/n times as high as the full scale input voltage at the input terminal 1.
AZUMA KOICHI
YAMAGUCHI HIDEHIKO
TOMARI NAOSADA
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