| 摘要 |
Voltage values at a high-voltage side and a low-voltage side of a reference voltage are generated on the basis of a current outputted from a current source circuit having an adjustable current value, and an impedance element having an adjustable impedance value which is connected to an operating amplifier, analog-to-digital conversion is carried out on the basis of the reference voltages, whether gain adjustment for the analog-to- digital conversion is necessary or not is judged according to the conversion result, and the output current of the current source circuit and/or the impedance value of the impedance element are adjusted on the basis of the judgment to adjust the generated voltage values at the high-voltage side and the low-voltage side of the reference voltage. The gain of the analog-to-digital conversion is made variable by adjusting the voltage values at the high-voltage side and the low-voltage side of the reference voltage. Therefore, it is possible to provide a gain-variable analog/digital converter which can maximize the performance of the analog/digital converter, and perform analog signal processing with high efficiency.
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