Three-stage GaN-on-SiC medium-power LNA exploiting a current-reuse architecture

A recently presented implementation of the current-reuse concept, specifically devised for microwave cascaded single-ended amplifiers, is applied to the design of a three-stage medium-power low-noise amplifier (LNA) operating in X-band. The LNA is realized on a GaN-on-SiC 0.25 mm technology supplied by Leonardo S.p.A.’s internal foundry and achieves a transducer gain (G T )of 24 dB, a noise figure(NF) better than 2.5 dB and an output power at 1 dB gain compression (P out,1dB ) higher than 20 dBm over the whole X-band. The first two stages of the LNA are stacked and share the same current while requiring, as a pair, a doubled external supply voltage, which corresponds to that of the third, medium-power stage. The versatility of the adopted current-reuse concept is exemplified by the fact that the two low-noise stages are initially designed in a conventional single-ended topology: only in a second step are they converted into a current-sharing stage pair with no significant effect on RF performance. Nonconventional approaches to low-noise design and small-signal stability analysis developed by the Authors and adopted in this design are referred to the Reader.