A 1.227 GHz low power single-ended input, differential output low noise amplifier (balun LNA) for GPS is proposed. A two stage structure with current-reused technique is adopted to achieve low power, low noise factor and high voltage gain simultaneously. The LNA is fabricated in 0.18 ??m CMOS process, consuming only 2 mA current from a 1.8 V supply. The LNA is measured to exhibit a differential voltage gain of 30.4 dB and a noise figure of 1.8 dB.