Superconductive JFET transistor is based on ability of the high-temperature ceramics super-conductors (e.g. YBa2Cu3O7) to become insulators when they do not conduct current.

Superconductor looses superconductive characteristic whenever electric or magnetic field penetrates into it. As the electric and magnetic fields perform pressure to Booze-Einstein superconductive fluid thus may be derived formula for the critical pressure at which the particular superconductor becomes insulator:




The pressure produced by electric field to the surface of a superconductor is defined by the following formula:




The device is controlled with the electric field. If it is known the critical intensity of Magnetic field at which superconductor becomes insulator than can be computed intensity of the electric field that produces the same effect by combining formulas (1) and (2):




For the known thickness d of superconductive film and intensity of magnetic field Bkr at which used superconductor becomes insulator, the appropriate potential that causes to device to change its state is:





d = thickness of superconductive film,

Bkr =intensity of magnetic field that breaks superconductivity,

ε0 = electrostatic permeability of vacuum,

cr = speed of electric field propagation in the superconductor,

The magnitude of voltage and consequently the intensity of electric field needed to control device could be significantly reduced by appropriate orientation of polycrystalline grains of a planar high-temperature superconductor and by adding appropriate impurities. The device is very similar to capacitor build on insulator (SOI technique) except that here between plates is superconductor with already reduced resistance to E-M field. Usage of superconductive plates (instead of Al ones) more resistive to E-M field than primary superconductor can reduce heating.

Schematic of the superconductive JFET device is shown on the picture bellow:




Dipl. Ing. Andrija Radovic´

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Author of this article and all its formulas is Andrija S. Radovic´, ©Andrija Radovic´, All Rights Reserved. The parts or whole article cannot be published without author's prior agreement and without author's name below the text.



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