A 286-GHz CMOS Amplifier Achieving 56-GHz BW3dB Via fmax-Boosting and Gain-Staggering

This paper presents a 286-GHz wideband amplifier implemented in a 28-nm CMOS process. To overcome the inherent maximum oscillation frequency (fmax) limitation of the process, a custom-designed NMOS layout is proposed, boosting the fmax from 378 to 415 GHz by minimizing gate resistance and implementing an optimized vertical drain routing scheme. A 16-stage differential amplifier, leveraging a stagger-tuned matching network based on transformers, is designed to realize a flat and wideband gain response. Measurement results demonstrate a peak gain of 18 dB, a saturated output power of 2 dBm, and a recorded 3-dB bandwidth of 56 GHz spanning 230 to 286 GHz. To the authors' knowledge, this is the first reported 300-GHz-band amplifier in 28-nm CMOS, paving the way for fully integrated terahertz system-on-chips in deep-submicron CMOS processes.