| 摘要 |
PROBLEM TO BE SOLVED: To provide a laser diode driving circuit for obtaining a stable light waveform even if luminescence property of a light emitting element changes. SOLUTION: A first S/H circuit 15 acquires monitor voltage (OFF level) when a laser diode 11 is put out. A second S/H circuit 16 acquires monitor voltage (ON level) at the time of light emission. LPF 17 acquires an average value (monitor average value) of monitor voltage. A duty feedback circuit 20 calculates an intermediate value (regular average value) from monitor voltage of the OFF level, monitor voltage of the ON level and a duty ratio (50%), and outputs a duty ratio control signal DSC so that the monitor average value becomes the regular average value. A duty control circuit 21 controls a waveform of data Txc based on the duty ratio control signal DSC. Thus, luminescence current Ip is controlled. COPYRIGHT: (C)2006,JPO&NCIPI
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