Abstract: Ultra-Wideband Low-Noise Amplifiers (UWB LNA) operating in the low-frequency band (3.1-5 GHz) of UWB spectrum are presented. The designs consist of a cascode amplifier with wideband input matching techniques based on LC-ladder filters or shunt-feedback both combined with inductive peaking. Implemented with a SiGe HBT process, the LNAs give 18.0 dB gain, better than-20 dB input matching and a return loss less than-34 dB, while consuming 11 mW under 1.5 V supply. The feedback LNA gives a better flat noise figure of 2.5 dB and an input IP3 of-6 dB at 5 GHz.