FOCAL POSITION SIGNAL DETECTING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To obtain a highly precise and stable focal position detection signal even in the recording format of a DVD-RAM, a PD or the like by muting an AGC circuit based on the detection signal of an address information part recorded on an optical disk and operating two pre-holding circuits. SOLUTION: An unnecessary response is suppressed by AGC-muting the transient response of an AGC by means of an ID signal at the timing of an ID part, and the signal after the detection of an envelope is pre-held in a first pre-holding circuit by means of a gate signal whose width is wider than that of a gate signal for muting the AGC. Thus, the highly precise and stable focal position signal is outputted from an RF signal accompanied with a very satisfactory ID signal by eliminating an overshoot due to the differential characteristic of a BPF pre-holding the unnecessary transient response caused in a BPF 16 in a second pre-holding circuit 17.