A Q-factor enhancement technique for MMIC inductors

An increase of 50% in the peak Q-factor and a wider operating bandwidth for monolithic inductors is achieved by exciting a microstrip structure differentially. Conventional excitation of a 8 nH spiral inductor fabricated in a production silicon IC technology resulted in a peak (measured) Q-factor of 6.6 at 1.6 GHz, while the differential connection showed a maximum Q-factor of 9.7 at 2.5 GHz. These experimental results compared favorably with the behaviour predicted from simulation.