Optical data medium driving apparatus and a servo circuit with normalization processing

Abstract

An optical data medium driving apparatus which constitutes amplifiers for an output current signal of photosensor by a plurality of current mirror circuits different in an amplification factor in order to switch in a wide range the output current signal of the photosensor which detects quantity of the reflected light corresponding to variation of the quantity of reflected light from an optical data medium having various characteristics, thereby obtaining the output with high accuracy and in a wide band, and a servo circuit which uses for an AGC circuit nomalizing a difference signal from each light receiving surface at a photosensor having a plurality of the light receiving surfaces an A/D converter which is given the difference signal as an analog input signal and the sum signal as the reference input signal and outputs an offset binary type digital signal, thereby being inexpensive to be produced, easy to be integrated and have high function, and high in reliability.

Dependencies are inferred from the claim text.