The operation of the self-balancing magnetic amplifier

FEEDBACK has been applied to amplifiers almost since their inception to alter the gain, bandwidth, impedances, etc. A combination of positive and negative feedbacks, decoupled from each other was applied to a vacuum-tube voltmeter by Gilbert.1 Geyger has reported on2 and patented3 a magnetic circuit similar in operation to the Gilbert circuit which has been designated the self-balancing magnetic amplifier. This amplifier has appeared in many forms. Voltage and current types, both single-ended and push-pull, are possible configurations. These amplifiers have been shown, experimentally, to have large power gains, linear output-input characteristics, and a high speed of response. Scorgie4 in comparing the self-balancing-type magnetic amplifier with the half-wave amplifier of Ramey has analyzed this circuit and reported that the speed of response can be made one half-cycle of the power supply frequency.