| 摘要 |
PURPOSE:To make the amplitude level constant by controlling the quantity of current of a current source in response to an error voltage. CONSTITUTION:A laser output control circuit 27 uses a monitor diode MD to monitor a laser output of a laser diode LD thereby detecting a difference voltage (error voltage) between a monitor voltage VMD extracted from a variable resistor VR and a reference voltage V1 outputted from a reference source E1. Then the quantity of current from a current source 11 is controlled variably in response to the error voltage to change the charging speed of a capacitor C1. Thus, a comparator CMP1 applies pulse width modulation (PWM) to a pulse output in response to the output of an error detection circuit 272.
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