Browse Prior Art Database

Josephson Read-Only Memory

IP.com Disclosure Number: IPCOM000047743D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Beha, H: AUTHOR

Abstract

A read-only memory (ROM) employing Josephson interferometers as bit storage cells is proposed in which the binary information ("0","1") stored in the cells is determined by the insertion point of the gate current fed to the interferometer. Fig. 1 shows the equivalent circuit of a current injection interferometer that can be used. It comprises 2 junctions with maximum Josephson currents I01 and I02 . Generally, the gate current Iy may be injected at any point (C) of the interferometer loop inductance L which is thereby divided into L1 and 12 . The injection point determines the value of p = L1/L. For the proposed ROM cells the gate current is applied to either point A or B, i.e., p is either zero or one. A control line, magnetically coupled to the interferometer loop, is provided to which a select current Ix can be applied.

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Josephson Read-Only Memory

A read-only memory (ROM) employing Josephson interferometers as bit storage cells is proposed in which the binary information ("0","1") stored in the cells is determined by the insertion point of the gate current fed to the interferometer. Fig. 1 shows the equivalent circuit of a current injection interferometer that can be used. It comprises 2 junctions with maximum Josephson currents I01 and I02 . Generally, the gate current Iy may be injected at any point (C) of the interferometer loop inductance L which is thereby divided into L1 and 12 . The injection point determines the value of p = L1/L. For the proposed ROM cells the gate current is applied to either point A or B, i.e., p is either zero or one. A control line, magnetically coupled to the interferometer loop, is provided to which a select current Ix can be applied. Fig. 2 illustrates how the interferometer threshold characteristic is affected by the choice of the gate current insertion point. It also shows the principle of the ROM operation. When read currents Iy and Ixare applied to the cell as indicated, the cell will remain in its zerovoltage state if a "0" is stored (p = 0) whereas it will switch to the voltage state if a "1" is stored (p = 1) due to the crossing of the threshold curve. The cells can be programmed either during device manufacture providing for gate current connections to points A (p = 0) or B (p = 1), or, after initially providing gate current connections to...