Monolithic inductor modeling and optimization

In English It has become a necessity to use on-chip inductors in radio frequency integrated circuits. Particularly oscillators need inductors to archive high performance. In LC oscillators the quality factor of the inductor is critical to the phase noise performance, and since the self-resonance frequency of the inductor will limit the operating frequency and tuning range of the oscillator, careful optimization is needed. As the transistors are scaled to smaller geometries, the supply voltage must be reduced. Since the inductors have almost zero DC voltage drop they can be used to increase the voltage headroom in low voltage RF circuits. For cross-coupled differential pair LC oscillators, an inductor at the source node of the differential pair will not only increase the signal headroom 1, but if resonating at twice the oscillation frequency it will also increase the phase noise performance significantly 2. The gain and noise factor of LNAs and mixers can also be improved by using inductors to tune out parasitic capacitances 3.