| 摘要 |
PROBLEM TO BE SOLVED: To provide a capacitance sensor circuit that can obtain voltages of capacitive elements independent of the temperature at the time of measuring. SOLUTION: A capacitance sensor circuit that detects signals each corresponding to one or another of n capacitive elements connected between a power source and the ground is provided with a switching unit 2 comprising n transistors of substantially the same size each of whose source ends is connected to one or another of the n capacitive elements, a constant current source 3 connected between the drain end of each of the n transistors and the power source, a leak current cancelling transistor M0 connected between the drain end of each of the n transistors and the power source, a detector 5 connected to the drain end of each of the n transistors, and a control signal generating circuit 4 that generates a control signal for turning off, when one of the n transistors of the switching unit 2 is turned on, the other transistors. Leak currents generated from the n-1 turned-off transistors are cancelled by the leak current generated from the leak current cancelling transistor M0. COPYRIGHT: (C)2012,JPO&INPIT |
