Shunt-coupled magnetic-amplifier circuits

A recent study of magnetic-amplifier theory based on block-diagram techniques1 suggested to this author that one potentially useful basic technique for extracting the output information from the simple self-saturating magnetic amplifier had been seriously neglected in the past. Although it is a well-recognized fact that the output information in a self-saturating magnetic amplifier is contained in the half-cycle average voltage across the gate winding, independent of power-supply variations, most of the conventional magnetic-amplifier circuits are so arranged as to make the output voltage proportional to the difference between the average gate voltage and the average supply voltage. (Subsequent to the preparation of this paper, Rosenstein published a description of a transactor2 which bears a family resemblance to the shunt-coupled circuit described in this paper.) The afore-mentioned study of the theory revealed that some definite advantages could be derived by utilizing the average gate voltage directly as the output quantity. One obvious advantage, of course, results from the fact that this “output voltage” is thereby made independent of the regulation of the power-supply voltage. More important advantages, however, can be realized when the gate voltage is used to drive a subsequent stage of a multistage amplifier. It is shown later that the application of shunt coupling to a 2-stage magnetic amplifier effectively circumvents the traditional interstage coupling problems and yields an amplifier with all the advantages and few of the disadvantages of conventional 2-stage amplifiers.