The design of a 2-V 900-MHz CMOS bandpass amplifier

Abstract

A 900 MHz low-power CMOS bandpass amplifier suitable for the applications of RF front-end in wireless communication receivers is proposed and analyzed. In this design, the temperature compensation circuit is used to stabilize the amplifier gain so that the overall amplifier has a good temperature stability. Moreover, the compact tunable positive-feedback circuit is connected to the integrated spiral inductor to generate the negative resistance and enhance its Q value. The simple diode varactor circuit is adopted for center-frequency tuning. These two improved circuits can reduce the power dissipation of the amplifier. An experimental chip fabricated by 0.5 mum double-poly-double-metal CMOS technology occupies a chip area of 500 x 500 mum(2); chip area. The measured results have verified the performance of the fabricated CMOS bandpass amplifier. Under a 2-V supply voltage, the measured quality factor is tunable between 4.5 and 50 and the tunable frequency range is between 845 MHz and 915 MHz. At Q = 30, the measured S-21 is 20 dB whereas the noise figure is 5.2 dB in the passband. The gain variation is less than 4 dB in the range of 0-80 degreesC. The dc power dissipation is 35 mW. Suitable amplifier gain, low power dissipation, and good temperature stability make the proposed bandpass amplifier quite feasible in RF front-end applications.