| 摘要 |
PROBLEM TO BE SOLVED: To provide an A-D conversion circuit inhibiting effects of a gain error and an offset error of a buffer circuit receiving an analog signal. SOLUTION: A reference circuit imparting a reference voltage comparing output voltages from the buffer circuits has first resistance voltage-dividing circuits (R1 to Rn) connected between two voltage-supply terminals (VRText and VRBxt) and supplying a reference voltage, second resistance voltage-dividing circuits (209, 210 and 211) connected in parallel with the first resistance voltage-dividing circuits between the voltage-supply terminals and buffers 201 and 202 using taps for the second resistance voltage-dividing circuits as inputs. The reference circuit further has an amplifier 203 amplifying a difference between one end (VRT3) of the first resistance voltage-dividing circuit and an output from the buffer 201 and the amplifier 204 amplifying the difference between the other end (VRT3) of the first resistance voltage-dividing circuit and the output from the buffer 202. The reference circuit further has a transistor 205 using the output from the amplifier 203 connected between VRText and VRT3 as the input and the transistor 206 using the output from the amplifier 204 connected between VRBext and VRB3 as the input. In the reference circuit, a comparator is supplied with reference voltages from both ends of the first resistance voltage-dividing circuits and intermediate taps. COPYRIGHT: (C)2007,JPO&INPIT
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