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Electronic Circuits Combining Superconducting Field Effect Transistors and Josephson Junctions

IP.com Disclosure Number: IPCOM000109629D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 95K

Publishing Venue

IBM

Related People

Chi, CC: AUTHOR [+2]

Abstract

It is known (1,2) that substantial electric field-effects can occur in the high-Tc superconductor YBa2Cu3O7-w. Also, superconducting fieldeffect transistors (FETs) have been suggested (3) which are based on such field-effects. Two electronic circuits are described herein which take advantage of the combined use of Josephson junctions and superconducting FETs.

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Electronic Circuits Combining Superconducting Field Effect Transistors and Josephson Junctions

       It is known (1,2) that substantial electric field-effects
can occur in the high-Tc superconductor YBa2Cu3O7-w.  Also,
superconducting fieldeffect transistors (FETs) have been suggested
(3) which are based on such field-effects.  Two electronic circuits
are described herein which take advantage of the combined use of
Josephson junctions and superconducting FETs.

      The circuit of Fig. 1 shows how superconducting FETs can be
used to reduce the noise of dc-SQUIDs by improving their read-out
schemes.  Bias-point modulation techniques have been successfully
applied to reduce parameter-noise in dc-SQUIDs (4,5).  These
modulation schemes are based on switching bias-flux and bias-currents
of the SQUIDs in the kHz regime.  Up to now, this electronic
switching process is done at room temperature with the corresponding
noise temperature.  In principle, the switching can be done at low
temperatures located spatially close to the SQUID by heating the
superconducting switches with laser irradiation. However, this
technique may suffer (6) from heat generated by the laser beam and
from trapped magnetic flux quanta.

      These problems can be avoided by switching the bias flux and
bias currents with superconducting FETs as shown in Fig. 1.  It is
pointed out that for the case of high-Tc SQUIDs, the FETs 1...4 can
be integrated on the same chip as the Josephson junctions 5, 6 and
fabricated in the same process.

      Fig. 2 shows a new inverting circuit...