Design and Optimization of Monolithic RF Transformers on Silicon

The generic stacked, bifilar, and nested coil designs of monolithic radio-frequency (RF) transformers on silicon are compared using the maximum available gain and the bandwidth as criteria of quality. As a result, the stacked-coil configuration has the best quality. Special attention is paid to ratioed stacked transformers which characteristic dependence on geometrical features is investigated and rules of design for effective turn ratio are presented. The results demonstrate the feasibility of using integrated ratioed stacked transformers in RF circuit design.