Common mode chokes (CMCs) are conventional circuit elements performing several tasks, including noise suppression, hindering electromagnetic interference, providing signal integrity, and circuit protection. Much as they are widely used, their fundamental construction and description are often qualitative and lack an understanding of the underlying physical principles. We discuss the behavior of a commercial CMC based on the physical description of the superparamagnetic core and parasitic circuit elements. The results are validated using a DC bias current and an external magnetic field, which affect the magnetic properties. The behavior of the CMCs in the strongly non-linear regime is also described.

7 pages, 6 figures