| 摘要 |
PURPOSE:To obtain a circuit for automatically adjusting an amount of light from a laser diode, which can reduce the number of external parts and pins and obtain an RF signal of an optimum level. CONSTITUTION:A signal level of an RF signal obtained by adding output signals from photodiodes 12-1 to 12-4 at an adder 15 is detected by a level detecting circuit 16. The detected level V1 is compared with a predetermined reference level V2 at a comparator 17. A driving current for a laser diode 11 is controlled by a driver 20 on the basis of a difference of the levels (V1-V2). |
