High data rate implantable wireless systems come with many challenges, chief among them being low power operation and high path loss. LNAs designed for this application must include high gain, low noise figure (NF) and better linearity at low power consumption within the required frequency. In this paper, our design is based on Impulse Response (IR) Ultra Wide-Band (UWB) operating at (3.1 — 5) GHz. We report the design and measurement of an LNA with 2.4dB NF, 17.3dB of gain and input intercept point of 2dBm consuming 4mW, which make it suitable for implantable radio applications. The process technology used here is 0.25µm CMOS Silicon on Sapphire (SOS) process.