| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve defects of a conventional electrostatic capacitor type fingerprint sensor device, to lower electric power consumption, and to reduce an offset voltage. <P>SOLUTION: This electrostatic capacitor type fingerprint sensor is provided with: a sensor electrode; a switching circuit for inputting a start signal for changing over a voltage to be impressed on an electrostatic capacitance generated between the sensor electrode and an object of detection; a charge-voltage converting capacitor for changing an output voltage in proportion to changes in charge; a switching circuit for inputting a start signal for setting an initial voltage at the charge-voltage converting capacitor; and a current mirror circuit for connecting the sensor electrode to a reference side and the charge-voltage converting capacitor to an output side. In the electrostatic capacitance type fingerprint sensor, the reference side of the current mirror circuit is provided with a switching circuit for inputting a hold signal for determining an output voltage generated by the charge of the charge-voltage converting capacitor in proportion to a charge which changes due to the changeover of a voltage impressed on the electrostatic capacitance generated between the sensor electrode and the object of detection, and the switching circuit and the current mirror circuit are constituted of a cascode type current mirror circuit. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
