Transformers, Inductors and Filters

Transformers, inductors and filters have continually played important roles throughout the field of electronics. Relatively crude electromagnetic devices were employed in early telephone and radio communication systems and today their vastly improved descendants are still found in most electronic systems. The sizes of electronic power transformers have been reduced through the development of new core materials and suitable hightemperature insulating materials. Design methods for audio and video transformers have been evolved which, in combination with improved core materials, made it possible to provide broad-band transformers having low distortion effects. Pulse transformers were developed for radar systems and made practical the hydrogen thyratron type pulse modulator. The performance characteristics of intermediate-frequency and radio-frequency transformers have been improved and their sizes reduced through the development of pressed-powdered iron and ferrite core materials. The linearity and stability of iron-cored inductors for filters have been improved through core materials development. Nonlinear inductors were made more nonlinear through the development of rectangular hysteresis loop magnetic alloys and ferrites, providing many new types of electromagnetic devices for electronic circuitry. Advances in electronics have made obsolete some applications of transformers and inductors but also have opened up other opportunities for inductive devices of novel or new characteristics.