A CMOS W-band amplifier with tunable neutralization using a cross-coupled MOS-varactor pair

This paper presents a CMOS W-band amplifier adopting a novel neutralization technique for high gain and stability. TheW-band amplifier consists of four common-source differential gain cells that are neutralized by a cross-coupled MOS-varactor pair. Contrary to conventional neutralizations, the proposed technique enables tunable neutralization, so that the gate-to-drain capacitance of transistors is accurately tracked and neutralized as the varactor voltage is adjusted. This makes the neutralization tolerant of capacitance change caused by process-voltage-temperature (PVT) variation or transistor model inaccuracy, which commonly occurs at mm-wave frequencies. The proposed tunable neutralization is experimentally confirmed by measuring gain and stability of theW-band amplifier fabricated in a 65-nm CMOS process. The amplifier achieves a measured gain of 17.5 dB at 79 GHz and a 3-dB bandwidth from 77.5 to 84 GHz without any stability issue. The DC power consumption is 56.7 mW and the chip area is 0.85 mm².