A High Gain-Bandwidth Product Distributed Transimpedance Amplifier IC for High-Speed Optical Transmission Using Low-Cost GaAs Technology

Baseband front-end amplifiers operating from DC to several GHz are required from high speed optical transmission systems. Classical direct-coupled baseband transimpedance amplifiers have high gain but their high frequency performance is limited by the parasitic capacitances of the transistors. Their upper frequency limit is empirically known to achieve only a 30% of the transition frequency (fT ) of the transistors (1). If we use commerciallyavailable 0.5 μm gate length GaAs MESFET's, which have the fT of 20 GHz, we can achieve only a 5-6 GHz bandwidth with such lumped element design technique. Moreover, the achievable gain is very often too low and need further amplification stages to satisfy the receiver specifications.