| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the received light power dependency of an output signal level of a receiver with a gain control function and to reproduce stable binary data. SOLUTION: A level detector 6 for detecting the level of preamplifier output signals S2 is provided and bias detection of a level corresponding to the optical output signals '0' of this receiver with a gain control function is performed with the above output. The level detector 6 turns a first peak detection circuit 7 to a sample mode when the output voltage of a preamplifier 2 is less than a fixed value, and turns it to a holding mode and holds detection output when it is more than the fixed value. An average value detector 14 detects the average potential of a positive phase output and an opposite phase output of a variable gain amplifier 3. A first comparator 9 amplifies difference between the output of the first peak detection circuit 7 and the output of the average value detector 14, and supplies it as an opposite phase input voltage to the variable gain amplifier 3. Thus, difference between the output of the first peak detection circuit 7 and the output of the average value detector 14 becomes a sufficiently small value and bias of the output signals of the variable gain amplifier 3 is stabilized. |
