| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical reception circuit for simplifying circuit constitution and lowering a cost. SOLUTION: In this optical reception circuit, an optical current I4 generated corresponding to the intensity of optical signals 29 made incident on a PD (photodiode) 20 connected through a protective resistor 21 to a power supply voltage VCC is detected for the portion of a voltage drop by the protective resistor 21 from the power supply voltage VCC and it is compared with a prescribed reference voltage. By the compared result, when the output of an invertible amplifier 24 is fed back to an input side, either one of the feedback resistors 26 and 27 of mutually different resistance values is selected by a switch 25. When the intensity of the incident optical signals is small, by enlarging a feedback resistance value, a feedback amount is enlarged and the gain of the amplifier is enlarged. When the intensity of the incident optical signals is large, by reducing the feedback resistance value, the feedback amount is reduced and the saturation of the amplifier is evaded. |
