Patent ID: 7787780

Claim:
An optical signal receiving circuit, comprising: a first transimpedance amplifier configured to convert a first current signal into a first voltage signal, wherein the first current signal is generated in a first photodiode, to which an optical signal is input; a second transimpedance amplifier configured to convert a second current signal into a second voltage signal, wherein the second current signal is generated in a second photodiode, to which an optical signal is input; a noise detection circuit configured to detect a noise signal of the second voltage signal, and configured to shift at least one of the first voltage and the second voltage to widen a voltage difference between the first voltage signal and the second voltage signal when the noise signal of the second voltage signal is detected; and a first comparator having as inputs the first voltage signal and the second voltage signal, and configured to generate a digital signal based on the first voltage signal and the second voltage signal, wherein the noise detection circuit includes: a reference voltage generation circuit configured to generate a reference voltage, and a second comparator that receives the second voltage signal at a first input terminal and that receives the reference voltage at a second input terminal; wherein the reference voltage generation circuit includes: a resistance connected between the output terminal of the second transimpedance amplifier and a node, a capacitance connected between a reference terminal and the node, and a voltage source connected between the node and second input terminal of the second comparator.