US Patent 7550700 Light-receiving semiconductor device and optical pickup device

According to an embodiment of the present invention, a semiconductor device used in an optical disk device driving an optical disk, includes: an optical pickup device detecting an optical signal irradiated to the optical disk and converting the detected optical signal into an electric signal to output the electric signal; and a light amount detecting circuit amplifying the electric signal output from the optical pickup device, the optical pickup device including a plurality of light receiving elements different in receiving sensitivity and the light amount detecting circuit including at least one amplifier or two or more amplifiers of the same amplifying characteristics.