An on-chip transformer in silicon-based technology

Abstract

The comprehensive characterization of a four-port transformer is investigated in this paper. The contents include the figure-of-merit, differential excitation and layout types. The coupling coefficient is added to the performance index of the transformer to characterize the device behavior. A foundry 90 nm CMOS technology is adopted to fabricate the on-chip transformers. Hence, the four-port measurement setup is executed to characterize the differential connection of the transformer. Furthermore, the layouts by maintaining identical self-inductance for both the planar and stack types are compared in the following items: coupling coefficient, transfer efficiency and chip area. Finally, an equivalent circuit is proposed to extract the model parameter in these transformers to investigate the high-frequency performance.