this work proposes an Ultra Low Power (ULP) digitally controlled LNA dedicated to Wireless Sensor Networks (WSN) implemented in a 0.13µm CMOS technology. Both optimized topologies and reconfigurable issues are investigated to save power consumption. Based on a self biased inverter, the circuit, operating under 0.6V, consumes 120µW and achieves a gain of 14.6 dB and a NF of 3.8 dB at 2.4GHz. To comply with the flexibility of the Wireless Sensor Network (WSN) in term of RF link budget variability, the core of the LNA can be reconfigured through a 3 bit DAC. Hence the gain and NF are 9.4 dB and 6.2 dB in the low gain mode, suited to cover a 10m range, consuming 30µW