LASER CURRENT DRIVE CIRCUIT

PURPOSE:To produce an offsetless laser current at a high speed in a source type laser current drive circuit in which a difference between a source current and a sink current makes an output current. CONSTITUTION:A sink current is so set as to be always higher than a source current 13 to input currents 16, 17 generated by switching a transistor 5 to a current path switching circuit made up of a transistor 9 and diodes 10, 11 provided in the front stage of a laser diode 12, thereby being able to produce an offsetless source current pulse because a sink direction current 16 generated when the transistor 5 is turned on is not discharged to a laser diode 12. Thereby, an offset current is prevented from being superimposed on a laser current.