MICRONWAVE APPLICATIONS OF SOLID STATE MATERIALS. 4. ANALYSIS OF INSTABILITY CRITERIA FOR MICROWAVE AMPLIFICATION IN FERROMAGNETIC MATERIALS. 5. AN EQUIVALENT CIRCUIT OF A MODIFIED SEMI-STATIC FERRIMAGNETIC AMPLIFIER

A general analysis is given of the criteria for parametric amplification by the use of a ferrimagnetic material. The results present a unified treatment of all three types of operation: the magnetostatic case, the semi static case and the electromagnetic case. Some of the results are at variance with results quoted in the literature. Also presented is a detailed analysis of an amplifier operating in the modified semistatic mode. An equivalent circuit is derived from first principles and the dependence of the threshold power on the geometrical and physical parameters of the system is obtained. It is shown that the threshold power may or may not depend on the sample shape depending on the orientation of the sample with respect to the dc field. For certain ranges of parameters no amplification is possible. (Author)