An ultra-low-power image-rejection low-noise amplifier (IR-LNA) for 2.4 GHz ZigBee applications based on 0.18 mu m CMOS technology is presented. By using the third-order active notch filter the proposed IR-LNA can achieve high image-rejection ratio. Measurements show 12 dB gain, 1.8 dB noise figure, 38 dB image-rejection, -3 dBm input third-order intercept point, -18 and -19 dB input and output return loss while dissipating 0.6 mA from a supply voltage of 1.5 V.