| 摘要 |
PURPOSE:To maintain photooutput power and photooutput waveform constant in a photooutput stabilizing circuit used for a digital light communication device using a semiconductor laser diode as a light source by correcting the temperature characteristics of a reference voltage for the deterioration of the controlling property occurred by the temperature characteristic of the dark current of a photodiode. CONSTITUTION:A voltage proportional to the mark ratio of a digital signal is produced from a drive circuit 3, applied to a voltage adder amplifier 8, a voltage proportional to the dark current is produced by a temperature correcting diode 7, added and amplified to obtain a reference voltage VR. Part of the photooutput of the diode 1 is received by a photodiode 2, the output VC of the average value detector 6 is compared by a voltage comparator 5 with the reference voltage VR, and a DC bias current to be applied to a semiconductor laser diode 1 through a current supply circuit 4 is controlled. The average value of the photooutput power is controlled to be completely proportional to the mark rate, maintained constant irrespective of the temperature change and ageing change, and the photooutput waveform is also maintained constant irrespective of the mark ratio. |
