Browse Prior Art Database

Configurations having Large Inductance for Use in Josephson Circuits

IP.com Disclosure Number: IPCOM000083304D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Landman, BS: AUTHOR [+2]

Abstract

Bridge devices which are composed of two or more Josephson junctions connected in parallel by inductances have been found to constitute low current, high-gain configurations to be used as logic and memory elements. The gain curve of these devices depends only on the LI(o) products, where L is the inductance connecting two junctions and I(o) the threshold current of those junctions. As the device current (approx.I(o)) is decreased, L must be increased. This is increasingly difficult if the device size is also decreased.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 2

Configurations having Large Inductance for Use in Josephson Circuits

Bridge devices which are composed of two or more Josephson junctions connected in parallel by inductances have been found to constitute low current, high-gain configurations to be used as logic and memory elements. The gain curve of these devices depends only on the LI(o) products, where L is the inductance connecting two junctions and I(o) the threshold current of those junctions. As the device current (approx.I(o)) is decreased, L must be increased. This is increasingly difficult if the device size is also decreased.

An example of a low-current device is a double bridge with a total threshold current of 0.1 mA and a gain of 2, in which the inductance must be L = 20pH. In single-flux quantum memory devices, the required inductance is even higher. L = 20pH corresponds to eight squares of line which are placed 2 micron above the ground plane.

Shown are configurations which employ holes in the ground plane to achieve the necessary inductances, without having to build devices that extend considerably out of the plane of the substrate.

The section of a line which crosses a rectangular hole in the groundplane, as shown in cross section in Fig. 1, will have an inductance per mil of length which to first order is given by: L(section) >/- 0.5 10/-11/ 1n(2d/lambda) in H.

Here lambda is the penetration depth of the superconductors. Thus, if the hole extends beyond the edge of the line by 0.5 mil as shown...