| 摘要 |
PURPOSE: To solve problems of a conventional phase comparator that has had difficulty of reducing a lockup time in the case of employing a passive filter and has increased harmonic spurious radiation or a phase noise of a VCO in the case of extending a loop band of a loop filter to enhance the lockup time. CONSTITUTION: A lock detector 22 increases a supply current of a 2nd current source 23b to increase a current of the phase comparator 20 when a PLL circuit 10 is unlocked and decreases or stops the supply current of the 2nd current source 23b to decrease the current of the phase comparator 20 when the PLL circuit 10 is locked so as to enhance the lockup time without extending a loop band of the loop filter 30 even in the case of employing a passive filter.
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