| 摘要 |
PURPOSE:To eliminate an influence of leakage current by providing a means for setting a potential drift at a contact due to the leakage current to an initial state. CONSTITUTION:If an input signal Vin is input to an operational amplifier 1, a voltage is impressed on an electrode 5 in such a way that a potential at a contact 3 becomes Vin. When a leakage current at a piezoelectric element 4 is more than that at a capacitor 2, the potential at the contact 3 rises. Accordingly, a potential at the electrode 5 drops, and a displacement amount at the piezoelectric element 4 decreases. When the leakage current at the piezoelectric element 4 is less than that at the capacitor 2, a reverse phenomenon occurs. During this process, a switch 8 is closed; the potential at the contact 3 is set to a ground potential; at the same time, the electrode 5 is set to the ground potential. If this operation is executed, an influence due to the leakage current can be eliminated. If an appropriate resistor R is inserted between switches 8, 9 and the ground, it is possible to prevent the piezoelectric element 4 from being broken down by an chance. |
