Analysis and Design of a CMOS UWB LNA With Dual- -Branch Wideband Input Matching Network

A wideband low-noise amplifier (LNA) based on the current-reused cascade configuration is proposed. The wideband input-impedance matching was achieved by taking advantage of the resistive shunt-shunt feedback in conjunction with a parallel LC load to make the input network equivalent to two parallel RLC-branches, i.e., a second-order wideband bandpass filter. Besides, both the inductive series- and shunt-peaking techniques are used for bandwidth extension. Theoretical analysis shows that both the frequency response of input matching and noise figure (NF) can be described by second-order functions with quality factors as parameters. The CMOS ultra-wideband LNA dissipates 10.34-mW power and achieves S ₁₁ below -8.6 dB, S ₂₂ below -10 dB, S ₁₂ below -26 dB, flat S ₂₁ of 12.26 ?? 0.63 dB, and flat NF of 4.24 ?? 0.5 dB over the 3.1-10.6-GHz band of interest. Besides, good phase linearity property (group-delay variation is only ??22 ps across the whole band) is also achieved. The analytical, simulated, and measured results agree well with one another.