Optimal Design of Inductively Degenerated Common-Source LNAs in Multi-Stage LNAs

new optimization method of first stage with inductively degenerated common-source stage in multi-stage LNAs is developed. This paper discusses the first stage source impedance optimization for minimizing overall Noise Figure (NF). Tow optimization method consist of conventional method and proposed one are compared for best overall NF performance. To validate obtained analytical results two different 10-12 GHz LNA have been designed based on proposed and conventional approach. In the first LNA its source impedance is optimized considering the effect of next stage’s noise while the second LNA is designed using conventional approach which optimizes first stage regardless to following stage’s noise. Post-Layout simulation results shows that consideration of subsequent stage’s noise in optimizing of LNA’s first stage leads to decrease in overall-NF without degradation in gain and impedance matching performance.