LASER DIODE PROTECTIVE CIRCUIT

PROBLEM TO BE SOLVED: To provide a circuit for protecting a laser diode from a surge current. SOLUTION: The protective circuit at least comprises an upper bound voltage limiter 100 which impresses predetermined voltage to the laser diode, and controls so that the voltage may not exceed more than constant value, and a voltage low-speed increaser 200 which increases gradually the voltage to be impressed to the upper bound voltage limiter by only predetermined time constant. When ATC (Automatic Temperature Control) is considered, the protective circuit may further comprise a lower bound voltage limiter which controls so that the voltage to be impressed to the laser diode may not fall below constant value, and a voltage low-speed deceaser which decreases gradually the voltage to be impressed to the lower bound voltage limiter by only predetermined time constant. COPYRIGHT: (C)2005,JPO&NCIPI