Dual-Channel 56 Gb/s PAM-4 Electro-Absorption Modulator Driver for 3D Wafer Scale Packaging

This paper presents the design and measurement of a $2\times 56\ \text{Gb}/\text{s}$ PAM-4 dual-channel electro-absorption modulator (EAM) driver in a $0.25-\mu \text{m}$ SiGe:C BiCMOS process for 3D wafer scale packaging. In this paper, a new EAM coupling method for 3D wafer scale packing is presented. The driver employs an optimized output interface with the EAM, which increases the output voltage swing by 53% while keep the same bandwidth and power consumption. The driver has 13.7 dB of gain with a 3 dB bandwidth of 31.5 GHz, which delivers $3 \ V_{ppd}$ at 56 Gb/s PAM-4 and consumes 364.5 $\text{mW}$ per channel, resulting in a figure of merit of 6.5 pJ/bit.