GB948453A - Improvements in or relating to logical circuits - Google Patents

Abstract

948,453. Logic circuits employing transistors and remanent magnetic cores. MULLARD Ltd. May 25, 1961 [June 1, 1960], No. 19410/60. Headings H3B and H3T. A logical AND circuit has its inputs A1, A2, Fig. 1, connected through transistors T1, T2 to opposed input windings W1, W2 on a core C of material having a rectangular magnetization characteristic, and an alternating output is induced in a winding W3 only when (a) both inputs are energized simultaneously by respective D.C. signals modulated by A.C. of opposite phase, (b) the two inputs are interlaced D.C. pulses which act in opposite senses in the windings W1 and W2, or (c) one input is a D.C. signal modulated by A.C. and the other a D.C. bias, each input being of sufficient value by itself to saturate the core. The core is unsaturated when an output is produced by coincident input signals, and the conducting transistors are arranged to bottom so as to obtain a substantially constant winding voltage and rate of change of flux. When one input only is energized, on the other hand, the core becomes saturated and the conducting transistor operates at a limited current value. An additional output winding W3<SP>1</SP> may be used to provide an output of opposite phase useful, for example, in cascaded logical circuits. In a modification, Fig. 3; providing the logical OR operation, winding W2 has parallel inputs A2 and A3, and an A.C. output is produced when a D.C. signal modulated by A.C. is applied to either or both inputs A2, A3, the input A1 being continuously biased by D.C. In a further modification, Fig. 4, a rectified feedback path to A2 which includes a smoothing circuit L maintains an output as long as a D.C. signal modulated by A.C. is applied to A1.