5. Nickel-zinc ferrites and their applications

Mn-Zn ferrites have high magnetizations but low electrical resistivities. This becomes a major drawback for applications at frequencies above 1 MHz. What's more, these materials are too "soft" to maintain high permeability at high frequencies. For frequencies above 1 MHz, nickel-zinc ferrites are chosen.

Ni-Zn ferrites are most often designed to operate at low induction levels for two main reasons:

• as operating frequencies are high (1 to 500 MHz), high voltages across the wound cores can be obtained for modest inductions; in fact, the peak voltage across a magnetic core of effective cross-section S and wound with N turns is given by:U = NSωB

• with ω pulsation Binduction peak ;

• At these high frequencies, the total losses dissipated by the material quickly...