High Turn Ratio and High Coupling Coefficient Transformer in 90-nm CMOS Technology

A novel layout of IC transformer is proposed to achieve both high turn ratio and coupling coefficient in this letter. Two groups of proposed devices are designed to maintain identical self-inductances in the transformer´s primary and secondary coils. A total of six devices are fabricated in foundry 90-nm CMOS technology. Using the nine and five metal layers in the primary and secondary coils in a specific layout, measurement results show that the proposed transformer simultaneously achieves high turn ratio and coupling coefficient with values of 1.9 and 0.89, respectively, in a 92-mum outer dimension.