An Analytical Consideration on an Equivalent Circuit of the Flux Distribution in Thin Film Cores

The flux distribution in certain inner-coil type thin film cores is discussed, and equivalent magnetic circuits for the distributed flux are derived based on the theory of distributed-constant circuits. The equivalent circuit has a simple structure and enables accurate determination of the core inductance. The validity of the equivalent circuit is demonstrated for a sandwich-type YIG inductor, which exhibits forty times the inductance of a similar air-core inductor. The equivalent circuit turns out to yield simpler expressions in cases where the in-plane magnetic path in the magnetic film is either very long or very short.