Noise figure analysis of 2.5 GHz folded cascode LNA using high-Q layout optimized inductors

The effect of inductor quality factor (Q) on the noise figure (NF) of a folded cascode low noise amplifier (LNA) is thoroughly studied for different values of DC power consumption. At lower power levels, the contribution of inductor Q towards the overall noise figure is shown to be less. Area optimized inductors with lower Q values can be used in such designs. However, for higher power levels, achievable NF is lower and is significantly affected by the Q of inductors. It is shown that layout optimized high-Q inductors can further reduce the NF by more than 10%. A 2.5 GHz LNA designed and simulated using 0.18 μm RF SOI process is shown to exhibit 1.4 dB NF while consuming 2.5 mW power with the return loss at the input and output better than 30 dB.