To meet low power requirements for Internet of Things (IoT) applications, the power dissipation of RF transceivers must be very low. As the Low Noise Amplifier (LNA) is one of the most energy consuming parts of an RF receiver, its power optimization is necessary for modern IoT devices. This work presents a 170 $\mu$W LNA capable of operating at 2.4 GHz when powered by a 0.4 V source. It is based on an inverter-based amplifier with improved gate bias voltage and automatic forward bulk biasing to operate at the moderated channel inversion level. A biasing metric is explored to analyze the best dimensions and bulk bias voltages for the NMOS transistor. Post-layout simulation results shown a 2.8 dB noise and competitive specification values compared to the state-of-the-art low-voltage LNAs.