Semiconductor laser drive circuit and photoelectric sensor

摘要

A photoelectric sensor and a semiconductor laser drive circuit (26) for a semiconductor laser element including a semiconductor laser drive diode and a monitor photodiode both having respective cathodes connected in common are disclosed. The semiconductor laser diode (30) has an anode connected to a power supply line (L1) side and the monitor photodiode (31) has an anode connected to a ground line side (G) via a voltage generating unit. The semiconductor laser drive circuit (26) includes a current control element (32), adjusting the amount of current supplied to the semiconductor laser diode, a feedback control unit (34) receiving a voltage signal generated by the voltage generating element (35) that is supplied to the current control element producing a control signal according to a level of the voltage signal maintaining the laser beam output at a predetermined level, and a biasing element (33) applying a reverse bias voltage to the monitor photodiode (31). <IMAGE>