| 摘要 |
PURPOSE:To obtain a change characteristic which is excellent in linearity and has less hysteresis by connecting a capacitor between the first electrode of a piezoelectric element and a reference potential, inputting the potential of this junction point to the negative-polarity input terminal of an operational amplifier, and using the signal from its output terminal to control the potential of the second electrode. CONSTITUTION:A capacitor 2 is connected between the first electrode 6 of a piezoelectric element 4 and a reference potential, said piezoelectric element consisting of a piezoelectric material, the first electrode 6 for applying a voltage to the material, and a second electrode 5. And the potential of the junction point between the capacitor 2 and the piezoelectric element 4 is inputted to the negative-polarity input terminal of an operational amplifier 1, an arbitrary signal Vin is inputted to the positive-polarity input terminal of the operational amplifier 1, and the signal from the output terminal of the operational amplifier 1 is used to control the potential of the second electrode 5. By connecting the capacitor 2 in series with the piezoelectric element 4 and storing a charge Q equivalent to the charge Q induced in the piezoelectric element 4 in the capacitor 2 in this fashion, Q of the piezoelectric element 4 can easily be known by detecting the voltage of the capacitor 2, and an arbitrary charge Q specified by Vin can be provided to the piezoelectric element 4 and maintained.
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