| 摘要 |
PURPOSE:To stabilize a laser output by using a photodiode which is connected between a field effect type transistor and a negative power supply line and also varies its current value by the laser light emitted by a laser diode. CONSTITUTION:When the laser output of a laser diode LD increases, the monitor current of a photodiode PD also increases. Then the gate voltage of a field effect type transformer FETF2 rises up to increase the drain current. Thus the potential of a common source rises up to deepen the bias of an FETF1. As a result, the drain current of the FETF1 is reduced and the base potential of a transistor TR Q5 rises up with reduction of the collector current. Then the emitter current of a TR Q6 is reduced. Thus the current flowing to the diode LD is reduced. An adverse function is actuated if the output of the LD is reduced to less than a reference level. Then the emitter current of the TR Q6 increases and the current flowing to the LD increases. The laser output is kept constant since the base-emitter voltage of the TR Q6 has no change. |
