Josephson memory cells having improved NDRO sensing

Details Josephson memory cells having improved NDRO sensing Josephson memory cells having improved NDRO sensing

1977-03-29

1978-12-19

Konick, Bernard

Static information storage and retrieval

Systems using particular element

Superconductive

307212, G11C 1144

Patent

active

041308930

ABSTRACT:
A superconducting memory cell which includes a single Josephson junction or write gate disposed in a superconducting loop having improved sense margins is disclosed. The improved sense margins are achieved by fabricating the superconducting loop so that first and second branches thereof have different inductances. In a specific example, a first branch containing the single Josephson junction has the higher inductance. Still more specifically, the inductance of the first branch containing the Josephson junction or write gate is twice as great as the inductance of the other branch when the I.sub.min of the write gate is zero. In addition, another Josephson junction or sense gate must be disposed in electromagnetically coupled relationship with the second branch of the loop, and binary information must be stored in the form of clockwise and counterclockwise circulating currents of equal magnitude. Writing and reading are accomplished by coincident currents being applied to the cell. A cell having a single control current in addition to a gate current for coincident current selection of a desired cell is shown. A similar cell having at least another control current in addition to the previously mentioned control current and a gate current for coincident current selection is also disclosed. The latter cell, embodied in array form, has a plurality of horizontally disposed control lines each of which intersects a row of memory cells. In addition, a diagonally disposed control line intersects the write gates of adjacent cells which are disposed in diagonally spaced relationship with each other. Arrays which include diagonal control lines have improved write margins and, if they conform to the criteria outlined above, they also have improved sense margins.

REFERENCES:
patent: 3402400 (1968-09-01), Sass
patent: 3491345 (1970-01-01), Gange
patent: 3987309 (1976-10-01), Hamel et al.
Sanborn, "Persistent Current Storage Cell", IBM Technical Disclosure Bulletin, vol. 3, No. 11, Apr. 1961, pp. 50-51.
Anacker, "Memory Cell Using a Single Josephson Tunneling Gate", IBM Technical Disclosure Bulletin, vol. 15, No. 2, Jul. 1972, pp. 449-451.

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