In this paper, we present a noise cancellation technique for common gate ultra wide band (UWB) low noise amplifiers (LNAs) which not only reduces the noise but also increases the gain. On implementing this technique in one of the existing UWB LNAs significant reduction of noise figure (NF) compared to same LNA without noise cancellation technique was observed. Noise cancellation of the most dominating thermal noise source viz. the input matching device with theoretical analysis is presented in this paper. Simulation results with TSMC 0.18 (m CMOSRF technology shows a peak gain of 28 dB and base NF of 3.16 dB for a 6.6 GHz (2.4-9 GHz) band LNA with noise cancellation when compared to peak gain of 21 dB and base NF of 4.09 dB without noise cancellation. Both theoretical analysis and simulation results are in good agreement. © Springer-Verlag Berlin Heidelberg 2013.