A differential low-noise amplifier (LNA) for the 5G n257 band and a frequency reconfigurable differential LNA for both the 5G n257 and n260 bands (26.5-29.5 and 37-40 GHz), fabricated in a 65-nm CMOS process, are presented. Both LNAs achieve better gain and noise figure performances due to the use of magnetically coupled gm-boosting in the common-gate stage of a cascode amplifier. Furthermore, the frequency-reconfigurable LNA uses frequency reconfigurable matching circuits at the input, interstage, and output to achieve optimal noise and gain matchings for each band. The single band LNA has a core chip area of 0.11 mm(2), a peak gain of 11.9 dB, a 3-dB bandwidth of 5.3 GHz, and a noise figure of 2.79 dB at 28.5 GHz. The dual-band LNA is capable of dual-band operation due to the reconfiguring matching circuits with switched coupled inductors (SCIs) and switched capacitors. It has a core chip area of 0.12 mm(2), peak gains of 11.1/8.5 dB, 3-dB bandwidths of 4.8/9.4 GHz, and minimum noise figures of 3.49/4.01 dB at 28.5/38 GHz, respectively.