| 摘要 |
PURPOSE:To obtain a leak characteristic of high accuracy by providing a first switch between a voltage holding capacitor and a leak capacitor, and also, providing a second switch on both ends of the leak capacitor, and opening and closing them alternately. CONSTITUTION:By opening and closing operations of once of the second switch 18 and the first switch 17, respectively, a value of a voltage held by a voltage holding capacitor 11 decreases in a prescribed ratio determined by the capacity C11 of the voltage holding capacitor 11 and the capacity C12 of a capacitor 12 for leak. When the number of times of the opening and closing operations of the second switch and the first switch, which are executed in a unit time is increased, that is, a period tc is shortened, the variation of the value of the voltage held by the voltage holding capacitor can be enlarged by that portion, and a virtual leak time constant can be made small. On the contrary, when the number of times of the opening and closing operations of the second switch and the first switch is decreased, the virtual leak time constant can be enlarged.
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