The Impact of Different Gain Control Methods on Performance of CMOS Variable-Gain LNA

CMOS technologies are widely exploited now in the design of LNA in a few-GHz range applications. Due to the increase of system dynamic range requirement, the design of variable gain LNAs (VGLNAs) has gaining its popularity. In this paper, the comparison of different gain control methods on performance of CMOS VGLNA is presented. The conventional cascode configuration LNA is considered for comparison due to its low NF, low power, and circuit simplicity merits. The comparison is made in terms of gain characteristic, NF, input and output matching, and linearity and is based on a standard 0.18mum CMOS technology and 3.3V supply voltage. Useful discussions and conclusions are drawn based on the comparison. The comparison results can serve as a useful design guide for selecting one of the gain control methods to meet different requirements for different application.