| 摘要 |
PURPOSE:To quicken the reply time when a level of an optical input signal of the optical reception amplifier circuit is suddenly changed. CONSTITUTION:The subject optical reception amplifier circuit adopting conventional automatic gain control (AGC) is provided with a peak level detection circuit 5 detecting a peak of an output of a variable gain control circuit 4, an interruption frequency filter 6 having a control terminal used to control an interruption frequency and interrupting a high frequency component of the output of the peak level detection circuit, a comparator circuit 7 comparing an output of the interruption frequency variable filter 6 with a reference voltage 8 and the configuration in which an output of the comparator circuit 7 is connected to a control terminal 41 of the variable gain amplifier circuit 4 and a control terminal 61 of the interruption frequency variable filter 6. Through this constitution, the cut-off frequency of the filter 6 interrupting the high frequency component is varied with the gain of the variable gain amplifier circuit 4 to quicken the processing speed of the automatic gain control system. |
