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In this paper, the performance limitation of common-gate LNAs (CG-LNAs) caused by short channel effects is presented. The analysis is based on equations, which describes the behavior of the MOSFET including the noise sources in all possible regions of operation. From these equations, the input time constant Tin is defined as one characteristic performance figure of the used CMOS technology. The bias dependent limitation of the noise figure NF and minimum input reflection coefficient min (S11,dB) is derived in dependence of Tin. The paper shows furthermore the advantage of biasing the CG-LNA in the moderate inversion region.