| 摘要 |
PROBLEM TO BE SOLVED: To provide a phase comparator circuit, capable of outputting a signal corresponding to a phase difference, even if the phase difference is small. SOLUTION: This phase comparator circuit is provided with a feed-forward circuit 4, between a frequency phase comparator 1 and a charge pump circuit 2. The feed-forward circuit 4 has capacitors C1 and C2 connected between respective Q output terminals of flip-flops 11 and 12 inside the frequency phase comparator 1 and the current route of the charge pump circuit 2. The capacitors C1 and C2 perform an operation for speedily supplying the Q output voltages of the D flip-flops 11 and 12 to the charge pump circuit 2, by capacity-coupling the Q output terminals of the D flip-flops 11 and 12 and the current path of the charge pump circuit 2. Therefore, even when the phase deviation between input signals FS and FR is small, a voltage corresponding to that phase deviation is supplied to the collector terminals of transistors Q1 and Q2 inside the charge pump circuit 2 and corresponding to the phase deviation, and a current flowing inside the charge pump circuit 2 can be accurately controlled. |
