| 摘要 |
PURPOSE:To prevent an output from being increased due to induced emission, by reducing a current value supplied for the driving of a LED by generating an output signal representing exceeding degree over a reference signal when the output signal of a light receiving monitor circuit exceeds a prescribed reference signal, from a comparator. CONSTITUTION:An end face light emitting type LED10 is constant current-driven by an input data pulse supplied via the base capacitor C1 of a transistor TR1 and a resistor R1, and emits light spontaneously. When the LED10 emitting the light spontaneously starts to move in the direction of the induced emission due to low temperature driving environment, the output light of the LED10 is increased. A signal representing the degree of increase is supplied to an operational amplifier 28 via a photodetector 22 and a low-pass filter 26, and is compared with the reference signal. The signal with a lower bias level enough to offset the increment of the output light is outputted from the operational amplifier 28, and moves the (0) level of an input data pulse string to the level, and suppresses the increase of the output light. |
