OPTICAL RECEIVER

摘要

PURPOSE:To suppress the residual output level control deviation within the specified value by providing a comparator comparing a mean terminal voltage of an avalanche photodiode with a reference value and a switch circuit switching the feedback resistor of an operational amplifier with a signal from the comparator so as to switch the loop gain in response to the range of the optical input level. CONSTITUTION:The loop gain of the circuit is proportional to the gain of operational amplifiers 9, 10 and the loop gain and the response speed suitable for the optical input level are switched by selecting feedback resistors 11-14. A current flows to the APD 1 by photoelectric conversion and a voltage corresponding to the mean value of the optical input level is generated at the anode of the APD 1. The voltage is fed to a window comparator 17, and when the optical input level is within a range (a) (Pr2 < optical input level Pr