| 摘要 |
According to an aspect of an embodiment, an apparatus comprises: a first current source and a second current source; a resistor connected between the first current source and a reference potential portion; a switched capacitor circuit having a variable capacitor, first switch and a second switch, the first switch and second switch alternately switching capable of charging a voltage to the variable capacitor and capable of discharging a electric charge of the variable capacitor; an integrating circuit having an output terminal and a first input terminal which is connected a portion between the second current source and the switched capacitor circuit, an integrating circuit for integrating a current from the portion and for exchanging into an output voltage of the output terminal; and a comparator for comparing the voltage between two end of the resistor and an output voltage of the integrating circuit.
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