| 摘要 |
PROBLEM TO BE SOLVED: To enable keeping an optical output of a laser constant, even if temperature changes and deterioration with time passage exist, in a laser drive circuit. SOLUTION: A current-voltage converting circuit 2 converts the output current of a photodiode 1 for monitoring the optical output of a laser LD into a monitor voltage Vivc. A transconductor 4 outputs an output current, corresponding to the difference between the monitor voltage Vivc and a prescribed reference voltage Vref. A drive current output circuit 6 outputs a laser drive current ILD, corresponding to a hold voltage VH of a hold capacitor 5 connected with the output side of the transconductor 4. Thereby, the feedback is so performed that the voltage Vivc becomes equal to the voltage Vref, and the optical output of the laser LD is always kept constant. Hence, stable APC (automatic/power/control) function of high accuracy is realized.
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