Linear Large-Swing Push–Pull SiGe BiCMOS Drivers for Silicon Photonics Modulators

The analysis, design, and experimental characterization of a novel class of large-swing low output-impedance push-pull SiGe BiCMOS drivers are discussed. The circuits, which employ singleand series-stacked emitter follower (EF) and MOS-HBT cascode topologies, are intended to drive optical modulators with high-order m-pulse-amplitude modulated (PAM) signals, while maximizing energy/bit efficiency. The series-stacked EF version, implemented in a 55-nm SiGe BiCMOS technology with 370 GHz fMAX, achieved the highest linearity with 4.8-Vpp differential output swing, 57.5 GHz bandwidth, and an output compression point of 12 dBm per side. Four-PAM and eight-PAM eye diagrams were measured at 56 GBd for a record data rate of 168 Gb/s. Four-PAM 64-GBd eye diagrams were also demonstrated. The circuit consumes 820/600 mW with/without the predriver and has an energy efficiency of 4.88/3.57 pJ/b.