Browse Prior Art Database

High Gain Josephson Device

IP.com Disclosure Number: IPCOM000077181D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Zappe, HH: AUTHOR

Abstract

A high-gain Josephson junction device 10, shown in lateral cross section, Fig. 1, has an asymmetric curve of maximum Josephson current I(m) versus applied magnetic field H. Due to this asymmetry, Fig. 2, a small change in magnetic control field H(c) will cause a large change in maximum Josephson current I(m). The generally symmetrical I(j) vs H dependency, Fig. 3, is transformed into this asymmetric curve by provision of an additional magnetic field penetrating junction 16 and instantaneously proportional to the actual Josephson current I(j) flowing through the device. This proportional field is generated by applying a current K(i)I(j), to one of the adjacent control lines, 26.

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High Gain Josephson Device

A high-gain Josephson junction device 10, shown in lateral cross section, Fig. 1, has an asymmetric curve of maximum Josephson current I(m) versus applied magnetic field H. Due to this asymmetry, Fig. 2, a small change in magnetic control field H(c) will cause a large change in maximum Josephson current I(m). The generally symmetrical I(j) vs H dependency, Fig. 3, is transformed into this asymmetric curve by provision of an additional magnetic field penetrating junction 16 and instantaneously proportional to the actual Josephson current I(j) flowing through the device. This proportional field is generated by applying a current K(i)I(j), to one of the adjacent control lines, 26. Control lead 28 carries a bias current I(b) to provide the magnetic bias field H(b) establishing the operating point of tunnel junction 16 near the edge of the I(m) characteristic, Fig. 2, and lead 24 will receive a current signal I(c) to switch device 10 from the zero voltage state to the voltage state when the field dependent I(m) value no longer exceeds I(j).

Fig. 4. shows how the characteristic for I(m) may be varied by different choices of the proportionality constant K(i). Fig. 5 shows the preferred embodiment, so designed that the full Josephson current I(j) is fed back to provide the proportional field, and K(i) = 1. In this case, the bias current I(b) is also carried by lead 24, or else the third control lead, 28 of Fig. 1, might be applied on top of the...