| 摘要 |
PROBLEM TO BE SOLVED: To provide a dropout detector circuit such that parameter modification can be performed readily without an external circuit and an analog circuit, it is not influenced from the extrinsic factors, such as a noise, and the optimum dropout detection can be performed to a reproducing speed. SOLUTION: A digital RF signal 14 is generated by an A/D converter 2 using an analog RF signal 1. A bright side envelope signal 12 is extracted from the digital RF signal 14 by a bright side detector circuit 5, and a dark side envelope signal 13 is extracted by a dark side detector circuit 6. A reproducing speed signal 36 of a disk is derived by a frequency counter 37, and further a gain parameter (I) 33 and a gain parameter (II) 34 are generated by a gain parameter formation circuit 35, respectively. The amplitude levels of the envelope signals are varied in response to the gain parameter (I) 33, by a bright side gain switching circuit 31 and a dark side gain switching circuit 32, respectively. A comparator level reference signal 11 is generated by a comparator level controlling circuit 3 using the signal in which the amplitude level is varied and the gain parameter (II) 34. The bright side envelope signal 12 and the comparator level reference signal 11 are compared by a comparator circuit 4, and dropout detection is performed.
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