40-Gb/s optical receiver IC chipset - including a transimpedance amplifier, a differential amplifier, and a decision circuit - using GaAs-based HBT technology

GaAs-based HBTs with an InGaP emitter were used to develop key components of a 40-Gb/s optical receiver: a transimpedance amplifier, a differential main amplifier, and a decision circuit. The frequency response of the transimpedance amplifier was flattened by inserting an RC series circuit at the input stage. As a result, the transimpedance amplifier module produced a well-opened 43-Gb/s eye diagram with 400 mVp-p dynamic range. The differential main amplifier and the decision circuit produced 43-Gb/s eye diagrams with a large dynamic range of 700 mVp-p, which is the first 40-Gb/s demonstration using GaAs-based HBTs. These three ICs are thus applicable to a 40-Gb/s optical receiver.