| 摘要 |
PURPOSE:To protect a laser diode from breakdown at a low cost by a method wherein a junction type FET is connected in series with the laser diode, and two constant voltage diodes are connected in parallel therewith. CONSTITUTION:The junction type FET2 is connected in series via a drain electrode D on the side of the anode of the laser diode 1. The value of the saturation current of the FET2 is contrived to be equal to the value B of forward directional current which generate the maximum light-output A in the safety operational range of the laser diode 1, or to become lower. On the other hand, the two constant voltage diodes 3 and 4 are connected in parallel with the laser diode 1 and the FET2 as back-to-back. When positive and negative currents are impressed on terminals 5 and 6, the withstand voltage E of the diode 4 selects a voltage whereby breakdown is not generated in a state that the drain current of the FET2 is saturated. |
