A 2.4 GHz low-noise low-power single-to-differential bandpass amplifier is implemented in 0.5 μm CMOS process. In this bandpass amplifier, the compact tunable positive-feedback circuit is connected to the integrated spiral inductor to enhance its Q value. The simple diode varactor circuit is adopted for center frequency tuning. Two parallel spiral inductors are used to reduce the effective inductance and raise the center frequency. HSPICE simulation has been performed to verify the performance of the designed bandpass amplifier. It has been shown that the amplifier has a gain of 15 dB at Q=45 under 2 V power supply with 39 mW power dissipation. The noise figure is 4.36 dB in the passband. The tunable frequency range is between 2.369 GHz and 2.422 GHz. The gain difference and phase difference between the two differential output nodes are 0.0011905 dB and 179.932° respectively, at 2.4 GHz.