| 摘要 |
PURPOSE:To prevent the deteriorating the destructing of a semiconductor laser by overlapping a high frequency current at the time of reproduction, and preventing the overlapping of the high frequency current at the time of recording. CONSTITUTION:At the time of reproduction, the output of an AND circuit 7 is 'L', and a base voltage V1 of a transistor Q1 is lower than a base voltage V2 of a transistor Q2 determined by resistances R2 and R3. Consequently, the transistor Q1 is OFF, Q2 is ON and at a semiconductor laser 1, an the current IR(reproducing electric current) determined by a current source 8 flows. At such a time, the high frequency signal oscillated by a high frequency oscillator 13 is supplied through transistors Q3 and Q4 and a capacitor C2 for driving the laser 1 and a high frequency current IOSC is overlapped to the reproducing current IR. On the other hand, at the time of recording, a gate voltage V1 of the transistor Q1 is larger or smaller than a gate voltage V2 of the transistor Q2 in accordance with a modulating signal (data) inputted to an SG terminal, and as a result, the transistor Q2 is turned ON/OFF. |
