The design of a 3-V 900-MHz CMOS bandpass amplifier

A new bandpass amplifier which performs both functions of low-noise amplifier (LNA) and bandpass filter (BPF) is proposed for the application of 900-MHz RF front-end in wireless receivers. In the proposed amplifier, the positive-feedback Q-enhancement technique is used to overcome the low-gain low-Q characteristics of the CMOS tuned amplifier. The Miller-capacitance tuning scheme is used to compensate for the process variations of center frequency. Using the high-Q bandpass amplifier in the receivers, the conventional bulky off-chip filter is not required. An experimental chip fabricated by 0.8-μm N-well double-poly-double-metal CMOS technology occupies 2.6×2.0 mm² chip area. Under a 3 V supply voltage, the measured quality factor is tunable between 2.2 and 44. When the quality factor is tuned at Q=30, the measured center frequency of the amplifier is tunable between 869-893 MHz with power gain 17 dB, noise figure 6.0 dB, output 1 dB compression point at -30 dBm, third-order input intercept point at -14 dBm, and power dissipation 78 mW