| 摘要 |
PURPOSE:To stably control the light output of a laser diode to a prescribed output value by inversely amplifying a differential current between a reference current of a current source and a photovoltaic current of a photodiode, feeding back it to the forward current circuit of the laser diode, and controlling it to a current value corresponding to the reference current. CONSTITUTION:Since a photovoltaic current Is of a photodiode PD is proportional to a light output Po, the current Is is detected to control to feed back the output Po, thereby controlling the light output Po at constant value. The output Po is controlled so that the detected current Is becomes equal to a reference current Iref to be constant. In other words, in the state of Is Iref, no a base flowing current to a control transistor Q1 is presented, and the transistor Q1 is turned OFF. This, a bias current Ib from a bias current circuit 5 flows to the base of a driving transistor Q2, which is thus turned ON, the maximum upper limit current specified by a current limiting resistor R1 flows to a laser diode LD to increase the output Po. |
