| 摘要 |
PURPOSE:To provide an optical receiver which is simple in circuit structure and capable of amplifying a photocurrent well without distorting it. CONSTITUTION:A first photodetector 2 and a second photodetector 3 both generating a photocurrent are provided in an optical receiver, a second photocurrent i2 outputted from the second photodetector 3 is compared with a reference current iS through a current comparison amplifier, and when it is found that the second photocurrent i2 is smaller than the reference current iS, an output current is set to zero, and when the second photocurrent i2 is larger than the reference current iS, the second photocurrent i2 is amplified as much as a current gain K and then outputted. In a differential amplifier 6, a difference between a first photocurrent i1 outputted from the first photodetector 2 and an output current from the current comparison amplifier is amplified and outputted. Therefore, when a photocurrent is small, only the first photocurrent is amplified, and when a photocurrent becomes large, a difference between two photocurrents is amplified, so that an excessive current large enough to make a differential amplifier saturated is prevented from flowing into it. |
