Transimpedance Amplifiers with 95GHz Transimpedance Bandwidth and 1.5% THD for 800G Coherent Optical Communications

In this work, a linearity enhancement technique is proposed for the output drivers in transimpedance amplifiers (TIA) used in coherent optical receivers. Analysis shows that a pseudo-differential driver has better linearity than the commonly used fully differential driver. This is verified with simulations and measurements. A 3-stage TIA (TIA3S) and a 4-stage TIA (TIA4S) are designed using this technique and fabricated in the GlobalFoundries 9HP+ 90-nm SiGe BiCMOS process. The TIAs achieve 1.50% and 1.59% total harmonic distortion, (THD), at 1 Vppd with >67 GHz and 95 GHz transimpedance bandwidth while consuming 190 mW and 260 mW. The application areas are in 800 Gbps coherent optical communication links.