This paper presents low-voltage circuit topologies for 40-Gb/s communications in 90-nm and 65-nm CMOS. A retiming flip-flop implemented in two different 90-nm CMOS technologies employs a MOS-CML Master-Slave latch topology with only two vertically stacked transistors. Operation at 40 Gb/s is achieved by a combination of low and high-VT MOSFETs in the latch. Full-rate retiming with jitter reduction is demonstrated up to 40 Gb/s. Low-power broadband amplifiers based on resistor-inductor transimpedance feedback are realized in 90-nm and 65-nm CMOS to investigate the portability of high-speed building blocks between technology nodes. Experiments show that the transimpedance amplifier based on the CMOS inverter can reach 40-Gb/s operation with a record power consumption of 0.15 mW/Gb/s. A comparison between CMOS technologies underlines the importance of General Purpose rather than Low Power processes for high-speed digital design.