The operation of the current-type self-balancing magnetic amplifier

SELF-BALANCING magnetic amplifiers1,2 employ feedback to produce extremely useful characteristics. The input impedance can be made to approach either zero or infinity, the transfer characteristic is linear, the response time is easily varied to the minimum delay of one-half cycle, and the drift can be low because of a high signal-to-noise ratio. Applications of these circuits are appearing in increasing numbers in the literature3¿6 but until recently an analytical study was not available because of the complexity of the feedbacks involved in their operation. A previous paper6 indicates the general principles of self-balancing operation and discusses in detail one type of self-balancing circuit, the voltage-type. The following discussion will pertain to the current-type self-balancing magnetic amplifier. This amplifier has an input impedance approaching zero and as such is of considerable interest as a summing amplifier for signals from various sources.