COMPENSATING METHOD FOR OFFSET OR DRIFT OR THE LIKE IN OPTICAL RECEIVING CIRCUIT

摘要

PURPOSE:To automatically compensate offset or drift by inputting a detected offset component to a differential amplifier in the amplifier used for an optical digital receiver so as to eliminate the offset component included in the input signal given to the differential amplifier. CONSTITUTION:The detected offset component is held by an integration circuit 8 and it is inputted to one input terminal 1a of the differential amplifier 1. An output signal (offset component inclusive) from a preamplifier 6 is inputted to the other input terminal 1b of the differential amplifier 1. Thus, the difference of both signals to be inputted (without offset component) is outputted from the differential aplifier 1 and it is inputted to one input terminal 3a of a compa rator 3. A reference voltage from a reference power supply 7 is given to the other input terminal 3b of the comparator 3. Moreover, part of the comparator 3 is fed back to the input terminal 3b of the comparator 3 through a feedback resistor R. The feedback is applied repetitively until the output voltage of the comparator 3 is identical to the reference voltage.