CMOS RF band-pass filter design using the high quality active inductor

A high quality-factor of active inductor has been implemented by using the 0.18 mu m 1P6M CMOS technologies in this work. By adding a feedback resistance and a regulated gain stage transistor into the conventional cascade-grounded approach, the quality-factor and performance of CMOS active inductor can be improved. This novel active inductor demonstrated a maximum quality-factor of 540 and a 3.2 nH inductance at 4.3 GHz, where the self-resonant frequency was 5.4 GHz. An active CMOS bandpass filter was also fabricated including this tunable high quality factor active inductor, per-forming an insertion loss of 0.2 dB and a return loss more than 32 dB with a tuning range from 3.45 GHz to 3.6 GHz. The input IP3 was -2.4 dBm, and the noise figure was 14.1 dB with a 28 mW dc power consumption.