| 摘要 |
A pulse width modulation and intensity modulation signal generating unit, based on input data, performs pulse width modulation and intensity modulation and generates a light emission instruction signal. An error amplifier forms a negative feedback loop together with a semiconductor laser and a light reception device which monitors light output of the semiconductor laser, the error amplifier controlling forward current of the semiconductor laser so that a light reception signal proportional to the light output of the semiconductor laser is equal to the light emission instruction signal. A current driving unit causes a driving current, according to the light emission instruction signal, to flow through the semiconductor laser as the forward current thereof, the driving current being generated so as to control driving of the semiconductor laser with a current of the difference or sum with the control current of the negative feedback loop. The pulse width modulation nd intensity modulation signal generating unit, the error amplifier and the current driving unit are formed as one chip of an integrated circuit.
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