| 摘要 |
From the time of power on, an output of a variable frequency generating circuit (5) is kept matching with the resonance frequency of a resonance circuit (1). When an object of detection comes into contact or to the vicinity of a detection electrode and the resonance frequency of resonance circuit (1) changes, a phase deviation is generated from the output of the variable frequency generating circuit (5). The deviation is detected by a phase comparing circuit (3), and a control circuit (4) changes a control voltage so that the oscillation frequency of variable frequency generating circuit (5) is changed to attain phase matching. This change is detected by a detection circuit (7), and presence/absence of the object is detected. <IMAGE> |
