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Microbridge Constant Current Regulators for Josephson Circuitry

IP.com Disclosure Number: IPCOM000082390D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 18K

Publishing Venue

IBM

Related People

Laibowitz, RB: AUTHOR

Abstract

Single-level metallurgy, all-metal microbridge devices are described, which have applications as constant-current regulators with small hysteresis for use in Josephson circuitry.

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Microbridge Constant Current Regulators for Josephson Circuitry

Single-level metallurgy, all-metal microbridge devices are described, which have applications as constant-current regulators with small hysteresis for use in Josephson circuitry.

A useful element for Josephson circuits is the constant-current regulator using a Josephson microbridge. A typical microbridge has the characteristic shown in the figure, wherein the constant-current region is labeled a. When the current exceeds Imax, the microbridge develops a voltage which is typical for most Josephson elements. The capacitance of the microbridge is very low, limited for the most part to stray capacitance which can be minimized.

When the external circuit parameters are readjusted, by sensing voltage, and the current is reduced, there will be little or no hysteresis effect in the retrace of the characteristic. This eliminates the need to cycle the supply current to the preset value.

When circuit parameters lead to hysteresis effects, the microbridge is operated closer to the transition temperature, T(c). In this region, hysteresis can be totally eliminated. Thus, Nb bridges with oxygen added approx. a few percent will have a depressed T(c), which can be adjusted to be slightly higher than the operating temperature, typically 4.2 degrees K. Alternately, a material such as V can be used which has a T(c) ~ 4.20 degrees K. In addition to small hysteresis effects, these bridges have such advantages as a single-l...