| 摘要 |
PURPOSE: A photo detecting device of an optical pickup is provided to automatically switch gains of write pulse and read pulse through switching control, when converting a current of a PD(Photo Detector) into a voltage, so as to prevent saturation upon writing, increase signals in a read section and improve an SN(Signal-to-Noise) ratio. CONSTITUTION: A current/voltage converting unit(300) and sample and hold circuits(301,302) are for photo detection. A write pulse generator(303) outputs a switching control signal to control gains of the current/voltage converting unit correspondingly to a write section and a read section. In the current/voltage converting unit, a PD(PD) is for photo detection. An operation amplifier(A1) converts a current value according to a receiving light amount of the PD into a voltage value. Resistances(Rx,Ry) decide gains of the operation amplifier. And a switching part(SW) selectively connects with the resistances by the switching control signal according to the write section and read section, to change a resistance value. |
