Patent ID: 9543906
Date: 2017-01-10
CPC Classifications: H03F

Claim:
1. An optical receiver to receive an optical signal, comprising: a photodiode to generate a photocurrent corresponding to the received optical signal; a first trans-impedance amplifier (TIA) to convert the photocurrent into a voltage signal, a second TIA having a same arrangement as an arrangement of the first TIA, the second TIA outputting a reference; a differential amplifier to amplify a difference between the voltage signal and the reference, the differential amplifier outputting two outputs complementary to each other; an offset canceller to extract a portion of the photocurrent based on the outputs of the differential amplifier; and a level detector to detect an average of the photocurrent, the level detector outputting a control current to the second TIA to vary the reference, wherein the first TIA and the second TIA each have a first stage amplifier including a first bipolar transistor and a second stage amplifier including a second bipolar transistor, the second stage amplifiers of the first TIA and the second TIA respectively outputting the voltage signal and the reference, wherein the second TIA receives the control current from the level detector, the control current varying a current flowing in the second stage amplifier of the second TIA, wherein the second stage amplifier of the second TIA includes a load resistor, the second bipolar transistor, and an emitter resistor connected in series between a power supply and ground, the reference being output as a voltage drop caused in the load resistor by a collector current flowing in the second stage amplifier of the second TIA, and wherein the control current is provided to the emitter resistor to decrease the collector current in the second stage amplifier of the second TIA.