In this paper, an ultra wide band (UWB) low noise amplifier (LNA) circuit with a new input stage is proposed. In this scheme, a combination of coupled inductors in the input stage is utilized. The input stage is able to easily reject out-band interference. This input stage is applied in an LNA with 0.18 μm technology. The LNA has a peak gain of 21.72 dB in 3.1-10.6 GHz frequency band while showing a minimum noise figure of 1.85 dB in the mentioned frequency band. This circuit rejects 15.2 dB out-band interference, while power consumption of the UWB LNA core is 11.8 mW DC which is supplied from a 1.8 V power supply. s11 is less than -10.3 dB over the entire bandwidth since the worst value of IIP3 over the entire bandwidth is -13 dBm, which occurs at the frequency of 10.6 GHz.