| 摘要 |
A capacitance/voltage conversion circuit converts the difference in electrostatic capacitance between a first capacitor and a second capacitor into a voltage. With such an arrangement, a first voltage applying unit applies a power supply voltage Vdd to the first capacitor during a first state, and applies the ground voltage 0V to the first capacitor during a second state. A second voltage applying unit applies the ground voltage 0V to the second capacitor during the first state, and applies the power supply voltage Vdd to the second capacitor during the second state. A first sample hold circuit averages the voltage at the first capacitor and the voltage at the second capacitor in the first state by turning on a first switch and a second switch, and holds the voltage thus averaged as a first detection voltage Vdet1. In the same way, a second sample hold circuit averages the voltage at the first capacitor and the voltage at the second capacitor in the second state, and holds the voltage thus averaged as a second detection voltage Vdet2. An amplification unit performs differential amplification for the first detection voltage Vdet1 and the second detection voltage Vdet2.
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