A Compact High-Gain D-Band LNA With Lossy Gain-Boosting Core Based on Slow-Wave Feedback

This article presents a CMOS D-band low-noise amplifier (LNA) employing a lossy gain-boosting core with slow-wave feedback. By accounting for the practical losses of the embedding elements, the proposed lossy gain-boosting core achieves a more reliable and precise maximum available gain ( $G_{\mathrm {ma}}$ ) than ideal lossless models. Each common-source (CS) stage effectively leverages the gain-boosting core for promoting $G_{\mathrm {ma}}$ while maintaining the unconditional stability of the LNA. Depending on the analysis of two noisy networks in parallel, the gain-boosting core also facilitates simultaneous noise and input matching. Through an in-depth discussion on the impact of the Q-factors of the embedding elements, slow-wave feedback featuring low loss and high characteristic impedance is applied to further promote gain and noise with a compact footprint. To demonstrate the feasibility of the proposed configuration, a three-stage LNA is implemented in a 40-nm bulk CMOS and measured. The fabricated LNA achieves a measured power gain of 18.4 dB, and a minimum in-band noise figure (NF) of 6.1 dB. In addition, the proposed LNA consumes only 17.1 mW of power and occupies a compact core area of 0.057 mm2.