| 摘要 |
PURPOSE:To prevent an excessive current from being developed and obtained a compact, also more reliable LD driving circuit by interposing a prevention circuit with a capacitor and electric resistance against an excessive current between outputs to a diode connecting with a FET gate and a differential amplifier. CONSTITUTION:An electric resistance Rj is connected to a space between a differential amplifier 3 and a diode D1 and a capacitor Cj is connected to a connection portion q between the resistance Rj and the diode D1 and then, other end of the capacitor Cj is connected to a power source Vee (negative source). Moreover, a reference voltage of an input terminal d is set so that an output voltage of the differential amplifier 3 can be almost equal to an initial set point of gate potential Vg. If gate power source Vgg and Vee as well as a source power source Vss are fed, a source potential immediately comes out Vs but a gate potential Vg once geos down from 0V to Vee due to electrical charge and discharge under electric action of the capacitor Cj and the resistance Rj and after that it gradually rises towards Vg. Thus, an excessive electric current does not flow to a collector of a FET 2 and also does not break a laser diode 1. |
