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Josephson Technology Full Adder Design With No Timing Restrictions

IP.com Disclosure Number: IPCOM000081699D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Herrell, DJ: AUTHOR

Abstract

A full adder using Josephson technology in which the tunneling gates have different switching thresholds is suggested. Josephson junction devices having different widths are utilized, so that the gain curve of each device is different. Thus, a given number of control current inputs have different effects on different devices, depending upon the device width of the tunnel barrier. Using this concept allows the design of a plurality of circuit functions.

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Josephson Technology Full Adder Design With No Timing Restrictions

A full adder using Josephson technology in which the tunneling gates have different switching thresholds is suggested. Josephson junction devices having different widths are utilized, so that the gain curve of each device is different. Thus, a given number of control current inputs have different effects on different devices, depending upon the device width of the tunnel barrier. Using this concept allows the design of a plurality of circuit functions.

Specifically, the sum function can be expressed as:

S(n) = C(n) (A(n) + B(n) C(n-1)) + A(n)B(n)C(n-1). and this can be implemented with the arrangement of Fig. 1. With this approach, advantage is taken that after reset all control lines will have zero current, and can only change in one direction (viz. 0 to 1) due to the inherent hysteresis of the Josephson gates. Here it is assumed that true and complement signals are available from the input registers. If the register design does not allow for this possibility, then at the first level of the logic a string of clocked inverters may be inserted.

The gates necessary for this design, without inverters, are schematically represented in Figs. 2 and 3, together with their gain curves which are plots of the gate current I(g) versus the control current I(c). Different points along the I(c) axis denote different units of control current.

Referring to Figs. 1, 2 and 3, it can be readily seen that any two inp...