| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit having a variation correction function, which obtains an output close to a desired value by suppressing a variation in output characteristic, irrespective of characteristic variation of a constituent element in manufacture. SOLUTION: An output signal fref' having a different phase in terms of a reference signal fref is obtained through a dummy circuit 13 which includes a capacitor having the same structure as that of a capacitor subjected to correction in a VCO circuit 11, a working circuit. The phase difference between the reference signal fref and the output signal fref' reflects the manufacturing variation of the capacitor subjected to correction. The phase difference is detected by a phase comparator circuit 14, and according to an output signal vpd therefrom, control signals vsw1-vsw4 are produced by a control signal converter circuit 15. A switch in the VCO circuit is changed by the control signals vsw1-vsw4 to control the capacitance of the capacitor subjected to correction. Thus, an operation in which a capacitance is close to that in design is attained, irrespective of the manufacturing variation of the capacitor subjected to correction. COPYRIGHT: (C)2004,JPO
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