A 460 Gb/s PAM-4 Linear Distributed Driver with 105 GHz 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 ohms) 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.