SEMICONDUCTOR LASER DRIVER AND DRIVING METHOD

摘要

PROBLEM TO BE SOLVED: To drive a multilevel semiconductor laser current stably with high accuracy at high speed by keeping a voltage being applied to the output section of a semiconductor laser driver at a constant level and setting the power supply voltage to minimize a voltage being applied to the output section within the operable range of the driver. SOLUTION: When a drive current is drawn out from the cathode side of a semiconductor laser 4, a voltage detecting section 21 detects the collector voltage of a transistor 18 at the output section of a laser driver. Output signal from the voltage detecting section 21 is the voltage comparion section 22 and compared with the voltage of a reference voltage supply 23 and comparison result is fed back to a power supply transistor 24 in order to control the collector voltage of the transistor 18 at a constant level during recording, erasing and reproducing operations. When the collector voltage of the transistor 18 is set at a minimum operable level, i.e., a minimum level causing no bottoming saturation, generation of heat in the laser drive current output section can be kept at a minimum level.