| 摘要 |
PROBLEM TO BE SOLVED: To perform an APC operation effectively without supplying a meaningless overcurrent to a light-emitting device. SOLUTION: If an APC select signal FA is set to an H level for starting the APC operation, a monitor voltage V<SB>A</SB>is immediately generated by a monitor voltage generation circuit 16A, and an error voltage V<SB>EA</SB>corresponding to a finite difference between the monitor voltage V<SB>A</SB>and a reference voltage V<SB>P</SB>is outputted by an error amplifier circuit 18A. However, an S/H circuit 20A is still in a hold mode until the monitor voltage V<SB>A</SB>reaches near the reference voltage V<SB>P</SB>, and a laser diode LD<SB>A</SB>is driven at a switching current I<SB>SA</SB>of the same current value as before the APC operation is started. Also, the S/H circuit 20A is switched to a sampling mode after the monitor voltage V<SB>A</SB>reaches near the reference voltage V<SB>P</SB>, to start a feedback control operation of a closed loop. COPYRIGHT: (C)2008,JPO&INPIT
|
