We describe an Ultra-Wide Band Low-Noise Amplifier (LNA) with a variable gain that works in the 4.0 GHz to 4.5 GHz frequency range and is made with off-the-shelf discrete components. This LNA has a 30 dB variable gain and a noise figure of 2.2 dB. It was initially designed to be used in a UWB testbed for measurement and algorithm validation purposes. There already exist several versions of a UWB LNA but many of them are made with custom designed integrated chips. We give the readers all the information they need to build their own IR-UWB LNA receiver.