Abstract-An Ultra Wide Band (UWB) Low Noise Amplifier (LNA) for 802.15.4a UWB PHY (physical layer) is proposed. The amplifier is designed using IHP Microelectronis CMOS 0.25 µm technology for lower price.The LNA area, power, and performance was optimized using the Genetic Algorithm (GA). The optimization goals included inductance values, power consumption, and performance in the frequency domain using S-parameters, then fine tuned in the time domain using the reference UWB pulses of the 802.15.4a standards. The LNA consumes around 10 mW excluding the output buffer stage, has a gain of 11 to 15 dB, a 1 dB compression point of −9 dBm, and five inductors with a total value around 10 nH.