| 摘要 |
PROBLEM TO BE SOLVED: To extend a range of a light receiving level of an optical signal and to reduce the power consumption. SOLUTION: The receiver is provided with a light receiving element 1, a monitor circuit 2 monitoring an optical signal received by the light receiving element 1, two stages of amplifier circuits 3 or over that amplify an electric signal outputted from the light receiving element 1, and a gain adjustment circuit 4 making a signal level of the electric signal stable. In this case, a gain of the 1st stage amplifier circuit 3 is variably controlled by using an output voltage of the monitor circuit 2. Furthermore, the 1st stage amplifier circuit 3 is provided with a through-circuit 5, a gain adjustment amplifier circuit 6 and a changeover device 7 to select either of both the circuits 5, 6 and when a level of an optical signal made incident onto the light receiving element 1 is a prescribed level or over, the signal received by the 1st stage amplifier circuit 3 is given to the through-circuit 5 and when a level of the optical signal made incident onto the light receiving element 1 is a prescribed level or below, the signal received by the 1st stage amplifier circuit 3 is given to the gain adjustment amplifier circuit 6. |
