| 摘要 |
PURPOSE:To attain stable AGC operation by providing a compensation circuit having a characteristic opposite to that of a photoelectric converting element and a variable gain amplifier and having a constant feedback loop gain to make the gain of the feedback loop over a broad range nearly constant. CONSTITUTION:A signal converted into an electric signal by the photoelectric converting element 1 is amplified by an AGC amplifier 2 and fed to an equalizer 3, a timing extracting section 5 and a level detecting section 6. A signal detected by the level detection section 6 is as address signal to a ROM13 constituting the compensating circuit 11. A control data giving an opposite characteristic to the characteristic of the photoelectric converting element 1 and the AGC amplifier 2 and a monitor signal data are stored in the ROM13 and a read data is processed by a control circuit 7 and becomes a control signal for the photoelectric converting element 1 and the AGC amplifier 2. Further, a signal converted by a DA converter 15 is outputted from a monitor terminal 10 as a monitor signal. |
