A 2-tap 40-Gb/s 4-PAM transmitter with level selection based pre-emphasis

This paper presents a 2-tap 40-Gb/s 4-PAM transmitter with level selection based pre-emphasis. The parallel input to the transmitter is pre-coded at low frequencies, so that the pre-emphasis tap injects different currents into the output node of the transmitter based on different level changes of the output signal. The proposed pre-emphasis suppresses overshooting and lowers power consumption. The test chip is fabricated in a SMIC 65-nm CMOS process and shows a 45.2 mW power dissipation while operating at 20-GS/s, which is equivalent to 40-Gb/s.