| 摘要 |
<p>A successive approximation AD converter comprises a voltage comparator having a first terminal which is connected to an input terminal for an analog signal via a sampling capacitor, and a second terminal into which a reference voltage is input from reference voltage supply section, a successive approximation register connected to an output terminal of the voltage comparator and a DA converter for converting data in the successive approximation register into an analog signal and inputting the analog signal into the first input terminal of the voltage comparator. The voltage comparator comprising two or more differential amplifiers connected in series via acapacitancepair, a first switch connected between the sampling capacitor and a first stage of the differential amplifiers, a second switch connected between a connection point between the first switch and the sampling capacitor and the reference voltage supply section and a third switch connected between a connection point between the first switch and the first stage of the differential amplifier sand the reference voltage supply section. When the input analog signal is sampled, the first switch is switched OFF, and the second switch and third switch are switched ON, and when a voltage comparison is executed, the first switch is switched ON, and the second switch and third switch are switched OFF.
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