On the feedback in magnetic amplifiers: II ¿ Combined magnetic and electric feedbacks

A previous paper1 has presented a steady-state and transient analysis of various types of feedback, magnetic or electric, applied to a self-saturating bridge or center-tap amplifier. This paper is a brief extension of that treatment to certain combinations of a positive magnetic feedback and a negative electric feedback as used by Geyger in ¿voltage-balance¿ and ¿current-balance¿ potentiometer-type amplifier circuits.2¿4 The essential principle of these feedback combinations is well-known: The positive magnetic feedback reduces the control winding current, while the negative electric feedback insures stability and linearity without modifying the current requirements of the control winding. Two examples are shown in the schematics of Appendixes I and II. (The symbols and terminology are those used consistently in reference 1 and shall not be restated in detail.)