A straightforward design technique for narrowband multi-stage low-noise amplifiers with I/O conjugate match

Low-noise amplifier (LNA) designers often struggle to simultaneously satisfy gain, noise, stability, and I/O matching requirements. In this article, a novel design technique, tailored for two-stage low-noise amplifiers, is presented. The proposed design method is completely deterministic and exploits inductive source degeneration to obtain a two-stage LNA featuring perfect input and output match together with low noise figure (NF) and a pre-determined gain, including stability analysis. A novel flowchart is provided together with the corresponding design chart that contains gain, matching, and stability information, therefore addressing all key figures-of-merit of a linear amplifier. The design chart is easily implementable in commercial Electronic Design Automation software, to aid designers in the difficult task of selecting the appropriate source degeneration inductor value. The noise performance, on the other hand, is the best possible since the matching networks are designed to provide the input of the two Field Effect Transistors with the optimum termination for noise. The design method is validated with two separate test vehicles operating respectively at Ka-band (26.5-31.5 GHz) and K-band (20.0-24.0 GHz). The realized Monolithic Microwave Integrated Circuits exhibit 18 dB gain for both versions, NF of 1.5 and 1.2 dB, respectively for the Ka-band and K-band version. Input and output matching are typically better than 12 and 15 dB.