Patent ID: 8188795

Claim:
A phase comparator used in a clock generation circuit which extracts a synchronized clock which is synchronized with an inputted reproduction signal based on reproduction data obtained by sampling the reproduction signal with a sampling means, the phase comparator comprising: a cross detection unit which receives the reproduction data obtained with the sampling means and a predetermined reference value, and detects a cross timing with which the reproduction data crosses the reference value; a polarity determination unit which receives the reproduction data, and determines a polarity of an edge of the reproduction data; a phase error calculation unit which receives the reproduction data, a cross timing signal outputted from the cross detection unit, and a determination result from the polarity determination unit, and calculates a difference between the reproduction data and a zero value at the cross timing as a phase error; and a filtering process unit which filters the phase error calculated by the phase error calculation unit with the timing detected by the cross detection unit to generate the reference value to be given to the cross detection unit.