A NOVEL ACTIVE INDUCTOR AND ITS APPLICATION TO INDUCTANCE-CONTROLLED OSCILLATOR

This paper describes a novel active inductor using a common-source cas code FET with an inductive feedback. A compact lossy active inductor, which consists of a common-source FET and a feedback resistor, was use d as the feedback inductor to achieve high Q-factor and tunability, as well as reduce the chip size. The fabricated active inductor achieved more than 100 Q-factors with the maximum value of 3400 over the frequ ency range of 200 MHz, in the vicinity of 1.7 GHz. Inductance was tune d from 9.6 to 56 nH at 1.7 GHz by the variation of the feedback resist ance of the lossy active inductor. Using this active inductor (as a fr equency-selective element in the resonator), a monolithic inductance-c ontrolled FET oscillator was fabricated, which demonstrated an 18% fre quency-tuning range from 1.73 to 2.07 GHz, with an output power range from -9.3 to -6.3 dBm.