A Single-Stage Feedback-Feedforward D-Band LNA in SiGe BiCMOS

This paper presents a compact and low-power D-band low-noise amplifier (LNA) implemented in 55 nm SiGe BiCMOS. The circuit is based on the cascode configuration, and to address the fundamental gain limitations that arise when operating near the transistor fmax and over a large fractional bandwidth, gain boosting is concurrently applied to both the common-emitter (CE) and common-base (CB) through a combination of reactive feedback and feedforward. The trade-off between gain-boosting and bandwidth is analyzed, and the amount of boosting is set to preserve broadband operation. The interstage and output matching networks keep the bandwidth by exploiting dual-resonance. The realized amplifier demonstrates 14.5dB gain over a 50-GHz bandwidth (116–166 GHz) and a minimum noise figure of 4.8 dB. The feedback network also enables dynamic DC power expansion, yielding a peak OP1dB of 2.8 dBm at 12.2 mW and a record 15.5% power efficiency. Compared to prior sub-THz LNAs in similar technologies, the proposed design demonstrates 3× improvement in figure-of-merit, validating the effectiveness of the design.