A magnetically coupled tunnel diode oscillator employing a square-loop core is analyzed. Particular emphasis is given to understanding the effects of small, yet inevitable, leakage inductances and the inductance of the dc source on the switching pattern of the tunnel diodes. The combined size of these inductances is found to be the determining factor that leads to many unusual switching phenomena encountered with the inverter. Included in these phenomena is the delayed switching of the tunnel diodes, which manifests itself in the formation of a quasi-square wave at the inverter output in what can be a serious loss in efficiency. Physical explanations and mathematical analysis which bring into focus the significant effects of these stray elements are presented.