Patent GB-944757-A (GB)
Title: Improvements in or relating to switching arrangements employing magnetic thin films
Inventor: WILLIAMS MICHAEL
IPC: H03K17/84
Filed: 1961-06-16
Abstract: 944,757. Circuits employing bi-stable magnetic elements. GENERAL ELECTRIC CO. Ltd. Sept. 14, 1962 [June 16, 1961], No. 21888/61. Heading H3B. Input and output storage elements each comprising a discrete region of an anisotropic magnetic thin film carried by a conductive sheet are coupled by a closed conductive loop, the state of magnetisation of the output storage element being switched by current induced in the closed loop when one or more input elements are rotationally switched at a sufficient rapid rate. As shown in Fig. 1, each element is defined in a magnetic thin film 1 having an easy axis 2 by the intersections of looped drive conductors 6, 7, 8, 9 with looped input and output conductors 4, 5, the input conductor linking with write drive conductors 6, 7, 8 to form three input elements and the output conductor linking with drive conductor 9 alone to form an output element. The coupling loop 3 overlies the input and output conductors so as to couple all the elements. Each discrete storage region is itself made up of a number of discrete storage spots on the film each defined by the intersection of single co-ordinate conductors. Information digits are applied serially to input conductor 4 in the form of positive and negative pulses respectively representing " 1 " and " 0," each digit being recorded in a different input element. The arrangement operates as an AND gate if one of the input digits consists of a positive " 1 " control pulse and as an OR gate if a negative " 0 " control pulse is applied. The timing of the various pulses is shown in Fig. 2, the serial input pulses 11, 13, 15 representing the digits " 1, 1, 0 " being applied to input conductor 4 and each digit being stored in a different input element by applying pulses 10, 12, 14 to the write drive conductors 6-8 in turn. The input pulses are partially in coincidence with and lag on the write pulses, so that the axis of magnetisation of each element is first rotated to the hard direction, and then falls back along the easy axis in a direction determined by the polarity of the respective input pulse. The output element associated with drive conductor 9 takes up a magnetic state, according to the input digit majority, when a drive pulse is applied to the conductor in association with lagging but overlapping coincident read pulses 18, 19, 20 in the write drive conductors 6-8, the steep wave fronts of the read pulses ensuring adequate induction in the conductive loop 3 which functions as the input conductor to the output element. An output pulse 23 is obtained in conductor 5 when a read pulse 22 is subsequently applied to conductor 9. Several arrangements may be connected in cascade; the output storage element of one comprising the input storage element of the next and so on. A shifting register is formed by using only a single input storage element in each of the cascaded stages. Constructional details are disclosed, Fig. 5, in which the magnetic thin film 26 and associated looped conductors 28, 30- 32, 36 and 38 are sandwiched between neoprene pressure pads 41, 42 secured by a clamping plate 43 and an aluminium base plate 40. Each of the looped conductors is earthed at one end to plate 40 and has the other end provided with a matching resistor 45-50. The thin film is backed by a polished aluminium substrate and comprises 80% Ni, 17% Fe, 3% Co of about 1600 Angstrom units thick. Aluminium foil looped conductors insulated by anodising are used.