Patent ID: 7509059

Claim:
An optical receiver, comprising: a light-receiving element that receives an optical signal and converts the optical signal into a current; a bypass element through which a portion of the current of the light-receiving element flows; an impedance element that converts a remaining portion of the current of the light-receiving element into a voltage signal; a voltage separation element interposed between the impedance element and the light-receiving element and arranged to separate the voltages on both sides thereof; and an automatic gain control circuit arranged to control the current flowing to the bypass element in accordance with the voltage signal from the impedance element; wherein the automatic gain control circuit includes an NPN-type bipolar transistor, the NPN-type bipolar transistor including an emitter that is arranged to receive the voltage signal from the impedance element and a base connected to an automatic gain control reference power supply, and the NPN-type bipolar transistor being arranged such that the current flows to the NPN-type bipolar transistor when the voltage signal reaches a predetermined value.