Patent ID: 7365302

Claim:
A photo detector IC used in an apparatus for optically recording/playback information, the photo detector IC comprising: an output circuit for supplying an output signal obtained through a light-to-voltage conversion; an output terminal to be connected to a flexible printed circuit board; and an impedance varying circuit provided between an output of the output circuit and the output terminal for adjusting an output impedance of the photo detector IC, without causing attenuation of a required signal bandwidth while suppressing occurrence of peaking when connected to the flexible printed circuit board, wherein the impedance varying circuit includes a plurality of parallel-connected switching circuits; each of the switching circuits includes: a field effect transistor having a drain connected to the output of the output circuit, a source connected to the output terminal, and a gate connected to an individual switching terminal, and a resistor connected in parallel between the drain and source of the field effect transistor; and the number of field effect transistors to be turned on in the switching circuits is adjusted by a signal on each switching terminal.