This paper presents a reconfigurable multimode low-noise amplifier (LNA) capable of single-band, concurrent dual-band, and ultra-wideband operation. The multimode operation is realized by incorporating a switched multitap transformer into the input matching network of an inductively degenerated common source amplifier. The proposed LNA achieves single band matching at 2.8, 3.3, and 4.6 GHz; concurrent dual-band matching at 2.05 and 5.65 GHz; and ultra-wideband matching from 4.3 to 10.8 GHz. The power gain is 14.7-16.4 dB, noise figure is 1.9-4.7 dB, and third-order intermodulation intercept point is -2- + 0.4 dBm across all bands. The chip was fabricated in 0.13-μm CMOS, and occupies an area of 1.04 × 0.7 mm2, and has a power dissipation of 6.4 mW from a 1.2-V supply.