| 摘要 |
PURPOSE:To decrease the effect of a stray capacitance of a feedback circuit by providing capacitors for chopper separately depending on the direction of a charge current flowing to them. CONSTITUTION:The capacitors Co1, Co2 for chopper are provided separately depending on the direction of the charging current, and only the Co1 is connected when an output of an operational amplifier A goes positive and only the Co2 is connected respectively when the output goes to negative. Then the Co1 is charged positive at all times and the Co2 is charged negative at all times respectively when viewed from the output side of the amplifier A. As a result, the stray capacitance Cs being parasitic to the Co1, Co2 respectively is charged positive or negative only at all times. Thus the feedback effect repeating charge/ discharge to the stray capacitance Cs alternately is not caused and the feedback effect is not almost subjected to the disturbance by the stray capacitance Cs. Then the effect caused by the stray capacitance Cs being parasitic to the feedback circuit is eliminated.
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