| 摘要 |
PURPOSE:To obtain a driving circuit for a laser diode having no erroneous operation by providing a voltage stabilizer for equalizing the voltages of the emitters of third and fourth transistors, between the base and the emitter of the fourth transistor. CONSTITUTION:A voltage stabilizer is so composed as to obtain VR1=RR2 when the voltage VR1 of the emitter of a Tr40 is applied to the one input terminal of an operational amplifier 60 provided between the base and the emitter of a Tr50 to be fed back, data of '1' and '0' is applied to the base of a Tr20, and a reference voltage Vref set to the intermediate between '1'. and '0' is applied to the base of a Tr30. When the data is applied to the base of the Tr20, a pulse current flows to the Tr20 and Tr30, a current equal to the peak value of a pulse always flows to the Tr40, and a voltage VR1 is generated across a resistor R1, but this is applied to one input terminal of an operational amplifier 60, the voltage VR2 of a resistor R2 connected to the emitter of the Tr50 is applied to the other input terminal. Then, VR1=RR2 is obtained. As a result, the erroneous operation of an LD current alarm circuit can be prevented. |
