| 摘要 |
<p>PURPOSE:To stably maintain the light outputting power of a light emitting diode (LD) even against a temperature change by providing a nonlinear temperature compen sating means which detects the ambient temperature and nonlinearly changes the amplitude value of a driving pulse current against the temperature change to an ampli tude controlling means. CONSTITUTION:This drive circuit for light emitting diode is provided with a sensor circuit 2 acting as a nonlinear temperature compersating means, the output of which is connected with an attenuation circuit 3 and which nonlinearly changes the amplitude value of a driving pulse current outputted from the circuit 3 in accordance with a change in ambient temperature, with the sensor circuit 2 and attenuation circuit 3 constituting an amplitude changing circuit 4 which changes the amplitude value of the drive pulse current against a temperature change. In other words, this drive circuit is constituted so that it can maintain the amplitude value of the driving pulse current at a lower level by detecting the ambient temperature by using a negative-characteristic thermistor, the characteristics of which is nonlinear against temperature, as a tempera ture sensor and enlarging the degree of attenuation of the circuit 3 in accordance with the magnitude of a detected voltage. Therefore, the light emitting power of an LD can be maintained stably against a temperature change.</p> |
