A 1.9~22.5 GHz wideband LNA based on the current-reused cascade configuration in 90 nm CMOS is reported. 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 BPF. The wideband output matching was also achieved by making the output network equivalent to a second-order wideband BPF. Theoretical analysis shows that both the frequency response of input matching and NF can be described by second-order functions with quality factors as parameters. The LNA dissipates 9.96 mW and achieves low and flat NF of 3.24±0.5 dB and high and flat S21 of 12.02±1.5 dB for frequencies 1.9~22.5 GHz. The corresponding FOM is 7.44 GHz/mW, one of the highest FOMs ever reported for an LNA with bandwidth around 20 GHz.