A Novel Active Inductor with Almost Simultaneously Constant L and Peak Q at Different Frequencies and Independent Q Tunability

A novel Active Inductor (AI) is presented that its inductance values L and the peak values of quality factor Q can be kept almost constant at different frequencies, and the Q factor can be independently tuned with respect to the inductance value L. The external voltage tuning terminal of the positive transconductor in the feedback loop of positive and negative transconductors building block is configured to compensate for the variation of inductance with frequency. And the external voltages of two building blocks, namely the multi-regulated cascode structure circuit and RC feedback network are jointly tuned to compensate for the variation of Q value with frequency. In addition, the variable capacitance in the RC feedback network is employed to tune the Q factor without affecting the inductance value, thus the independent tuning of the Q with respect to the inductance value is realized. Based on TSMC 0.18ȝm CMOS process, the novel AI is verified by Advanced Design System (ADS). The results show that under the frequencies of 0.75GHz, 1.85GHz, 3.00GHz, 4.10GHz, the novel AI achieves the peak Q values of 999, 1003, 999 and 1001 respectively with the peak Q variation of only 0.40%. At the same time, the corresponding inductance values are 316.0nH, 310.2nH, 309.6nH and 303.1nH respectively with the inductance variation of only 4.17%. Moreover, the Q factor can be tuned from 610 to 1500 at each of the above four frequencies with negligible variation of inductance.