| 摘要 |
PURPOSE:To prevent malfunction and to improve the linearity by providing a buffer amplifier between an input switch and a coupling capacitor in a comparator in a converter using the AC coupling type comparator so as to eliminate spike noise appearing at the input signal terminal and eliminating fluctuation of a reference potential. CONSTITUTION:Buffer amplifiers 68-74 are provided respectively between input switches 47-60 and capacitors 40-46 in each comparator each consisting of inverters 33-39, the coupling capacitors 40-46 in each comparator each consisting of inverters 33-39, the coupling capacitors 40-46 band the switches 40-67. Through the constitution above, the spike noise synchronously with the clock appearing at the input signal terminal of the converter is reduced and the A/D conversion error due to the fluctuation caused by the noise is prevented, and it is not required to provide a current to charge the coupling capacitor again at each reference potential input point so as to improve the linearity of the A/D conversion and the conversion speed. In this case, complementary MOSFETs are used for the buffer amplifiers so as to attain small and simple circuit constitution.
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