| 摘要 |
PURPOSE:To prevent the generation of excessive current, deterioration and breakdown of a diode by installing a protective circuit to the output of an error amplifier. CONSTITUTION:A laser diode 1, a monitor PD, an error amplifier 2, a protective circuit 3, and a bias current generation circuit 4 constitute a negative feedback loop and operate so that the light output of the laser diode may be constant. As negative feedback control is not exercised while the power is supplied, the output voltage 20 of the error amplifier 2 may exceed an optimum value. The protective circuit 30 protects bias current control voltage 30 so that it may not exceed the optimum value even when output voltage 20 rises rapidly, thereby preventing excessive bias current from flowing to the laser diode 1. It is, therefore, possible to prevent excessive electric current from being supplied to the laser diode 1 and to protects the laser diode 1 against its deterioration and breakdown as well. |
