| 摘要 |
PROBLEM TO BE SOLVED: To provide an electronic circuit for sensing a capacitance change in a measured capacitive element with high accuracy while compensating dispersion in FET characteristics. SOLUTION: The electronic circuit of this invention is provided with: a transistor TR 5 for outputting a current corresponding to a voltage change supplied from a variable voltage source V<SB>dd</SB>via the measured capacitive element Cs to a current control terminal by means of capacitive coupling; a constant current source 22 for outputting a reference current; and a current sensing circuit 23 for sensing an output current level outputted from the transistor TR 5. The electronic circuit passes the reference current through the transistor TR 5 to compensate variations in a threshold voltage, brings a switching element TR 2 to an off state to make a current path between a gate and a drain of the transistor TR 5 nonconductive, changes a voltage applied from the variable voltage source V<SB>dd</SB>to the gate electrode via the measured capacitive element Cs and allows the current sensing circuit 23 to sense the output current level to obtain the capacitance change of the measured capacitive element Cs. COPYRIGHT: (C)2004,JPO
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