GB1080255A - Current driver for writing information into a magnetic core memory system - Google Patents

Abstract

1,080,255. Transistor switching circuits; circuits employing bi-stable magnetic elements. GENERAL PRECISION Inc. June 21, 1965 [July 20, 1964], No. 26052/65. Headings H3B and H3T. A current driver for a magnetic memory core directs the current from a constant current source selectively in one or other direction through the memory and limits the voltage across the memory during build-up of the current therein. In the circuit shown, to supply a half amplitude pulse to the core X or Y lines connected between 78 and the respective junctions of diodes 36 and 38, one pair of the pairs of transistors 40, 24 and 22, 34 is made conductive according to the required direction of the pulse. The corresponding transistor of an emitter coupled pair 10, 12 is then made conductive and when noise due to the transistor switching has subsided a corresponding one of 26 and 32 is rendered conductive. The base of the conductive one of transistors 10 and 12 is clamped through diode 60 or 62 to the voltage of a Zener diode 58 and, as initially the transistor saturates, this voltage is also applied to the cores. Current builds up until it reaches a value equal to the emitter current of the transistor whereupon the transistor becomes unsaturated and a constant current flows to the cores. Diodes 64 and 67 clamp the emitter voltage of transistors 10 and 12 and diodes 72, 74 and 76 provide a fixed emitter voltage for 26 and 32. Other planes of the core matrix are supplied by further sets of transistors 22, 24, 34, 40 connected to transistors 10, 12, 26, 32 which are common to all planes.