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Abstract

A small capacitance change detection device includes a capacitance detection element, signal generation circuit, signal amplification circuit, and output circuit. The signal amplification circuit includes a first transistor and first to third voltage sources. The second or third voltage source is connected to the other output terminal of the first transistor via a first switch. A voltage to be applied from the second voltage source to the other output terminal is set to have a value equal to or larger than a value obtained by subtracting a threshold voltage of the first transistor from a voltage of the first voltage source while a voltage to be applied from the third voltage source to the other output terminal is set to have a value equal to or smaller than a value obtained by subtracting the threshold voltage from the voltage of the first voltage source. The output circuit is connected to a connection point between the other output terminal of the first transistor and the first switch and, after a voltage of the second or third voltage source is applied to the connection point in an ON state of the first switch, receives the voltage at the connection point on the basis of an OFF state of the first switch and charge control by the signal generation circuit after the first switch is turned off.

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First Claim