A 56-Gb/s 0.39-pJ/bit PAM-4 Transmitter Frontend with Shunt-Ffe Tail-Less Driver and External Bias-Tees. - Yooseong Jang; Seokmin Yun; Jeonghyu Yang; Taeho Shin; Eunji Song; Jaeduk Han (ISCAS, 2025)