The in-line cryotron

Abstract

This paper describes a new type of planar thin-film cryotron namely, an in-line cryotron, and compares its advantages to the crossed-film cryotron. This cryotron has its gate and control elements superimposed and parallel, or in-line, whereas the crossed-film device has its gate and control elements crossed at right angles. The gain curve for the in-line cryotron has a region where incremental gains of one to ten may be obtained without a change in the gate-to-control width ratio Wg/Wc whereas large gains are not possible for the crossed-film cryotron without altering the width ratio. Larger gate resistances are possible within the in-line cryotron and calculations are given to show it is feasible to properly terminate low impedance strip transmission lines with characteristic impedances in the range of 0.1 to 1.0 ohms. It is necessary to properly terminate the strip transmission lines commonly used in superconducting circuit fabrication in order to achieve the maximum circuit switching speeds. Other advantages and the disadvantages of the in-line cryton are also discussed.