A High-Speed Linear Modulator Driver for 200-GBd PAM-4 with Low Group Delay Variation in 130-nm SiGe BiCMOS

A linear distributed modulator driver (DRV) designed and fabricated in a 130-nm SiGe BiCMOS technology with hetero-junction bipolar transistors (HBTs) capable of a fT/fmax of 350 and 450 GHz is presented for short-distance links up to 200 GBd PAM-4 to be integrated with Mach-Zehnder modulators (MZMs) or electro-absorption modulators (EAMs). The driver is designed to maintain a flat group delay variation of ±1 ps up to 150 GHz while providing a low-frequency gain of 10.8 dB and a 3-dB bandwidth of 80 GHz. At the 1-dB compression point and an input power of 0.5 dBm a voltage swing of 2.5 Vppd is achieved with a total harmonic distortion (THD) of 5 %.