Review of various realizations of integrated monolithic transformers

Abstract

The integrated transformer is an essential component in many RF integrated circuits. Planar and stacked transformers on a silicon substrate are widely used in low-noise amplifiers, active mixers, voltage control oscillators, filters, etc. This paper gives an overview of different configurations of integrated transformers, their layouts and fundamental electrical characteristics. This review, also, compares the advantages and disadvantages of various integrated monolithic transformer realizations regarding the occupied area on chip, the coupling coefficient, the inductances values and the parasitic effects. Some possibility for improvement of transformer performances, such as using patterned ground shield or design structures with variable width of turns in the primary and secondary winding are proposed, too.