A 28Gbaud/s 4Vpp PAM4 MZ Modulator Driver in 0.13\mu \mathrm{m}$ SiGe BiCMOS Technology

A 28Gbaud/s PAM4 large-swing optical modulator driver is designed in 0.13-μm SiGe BiCOMS technology. The designed driver includes variable gain amplifier, continuous time linear equalizer and main driver stage. Group delay peakpeak value and bandwidth bottleneck from MZM are challenges to achieve high speed optical interconnect at 28Gbaud/s. A compensation technique of de-emphasis and preemphasis is also adopted to reduce group-delay variation and broaden bandwidth, respectively. Simulation results show that the driver features gain of 20dB, -3dB bandwidth of 25GHz by utilizing pre-emphasis circuit and CTLE, and it delivers a differential output swing of 4Vpp. The group-delay variation of the driver is 3.1ps by using de-emphasis circuit, which is less than ±0.1UI.