Analysis and design of a high-Q differential active inductor with wide tuning range

The analysis and design of a high-Q differential active inductor with wide tuning range is presented in this study. The self-resonant frequency (SRF) and quality factor (Q) of the inductor can be tuned independently. The inductor was implemented in a 0.13 μm CMOS process. The measured SRF is tunable from 0.5 to 10.2 GHz. The obtained maximum quality factor is as high as 3000. The analysis shows that higher inductance corresponds to higher inductor noise while the correlation between quality factor and noise is relatively weak. Measurement results confirmed these predictions. The measured results show that this inductor structure is suitable for broadband reconfigurable radio-frequency system development. Further analysis and measurements show that the inductor is intrinsically non-linear, so are gyrator-C-based active inductors in general. A compensation circuit is proposed to improve the linearity characteristics of such inductors.