A 460Gb/s PAM-4 Linear Distributed Driver with 105GHz BW for TFLN Modulators in 130nm SiGe BiCMOS

We present a linear single-ended distributed driver implemented in 130nm BiCMOS process with fT / fmax of 470/650 GHz, designed for single-ended push-pull thin-film lithium niobate (TFLN) traveling-wave Mach-Zehnder modulators (TW-MZMs). High-linearity and low group-delay variation are achieved by using 10 cascode gain cells with large emitter degeneration resistors (23.5 Ω) and no capacitive peaking. The driver delivers an overall gain of 14.5 dB, a bandwidth of 105.7 GHz, and an output swing of 2.25 Vpp. Time domain experiments demonstrate 232 Gbaud PAM-4 (464 Gbps gross aggregate rate) with the use of offline DSP.