| 摘要 |
PURPOSE:To prevent excessive current flowing in a semiconductor laser, even if a power supply voltage instantaneously increases, by inserting and connecting the respective capacitors between the base of a last stage transistor of a constant current circuit provided with an APC function, and the base of a transistor constituting a constant current supply of a current switch circuit, and a power supply or earth. CONSTITUTION:Capacitors C1 and C2 are connected, respectively, to the base of a last stage transistor Q4 of a constant current circuit provided with APC function, and the base of a transistor Q3 of a current supply of a current switch circuit. By these capacitors C1 and C2, the base potentials of the respective transistors Q4 and Q3 are not varied, and the destruction of semiconductor laser LD is prevented, even if an instantaneous excessive voltage generates in the power supply voltage Vcc. Further, the wave distortion caused by slow response of a photo diode PD is smoothed by the capacitor C1, and has no effect on the light output P0. |
