| 摘要 |
PURPOSE:To constantly maintain the photooutput of a diode in spite of having variations in threshold voltage of a laser diode by a method wherein the parameter, with which the aimed control value of photooutput will be dtemined, is controlled in accordance with the working current of the diode. CONSTITUTION:The working current ID flowing to the laser diode 1 is detected and the reference voltage (VR), which is the positive-phase input of a differential amplifier 4, is controlled in accordance with the detected current. In order to accomplish the above function, a differential amplifier 7 is provided, and the voltage of the emitter resistor R4 on a transistor 2 is divided by resistors R5 and R6 and sent to the positive-phase input of said amplifier 7. A reference voltage VR1 is supplied to the negative-phase input of the differential amplifier through the intermediary of a resistor R8. This output of the amplifier 7 is turned to the positive-phase input of a differential amplifier 4. The setting current I1 of a monitor diode 3 is determined by the formula of calculation using reference voltage VR1 and resistors R7 and R8 only, and it is brought to a constant state, thereby enabling to bring the control command value of photooutput of the laser diode 1 into a constant state. |
