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ST184 - Voltage Biased Superconducting Quantum Interference Device Bootstrap Circuit

Voltage Biased Superconducting Quantum Interference Device Bootstrap Circuit

Xiaoming Xie1, Yi Zhang2, Huiwu Wang1, Yongliang Wang1,
Michael Mück3, Hui Dong1,2, Hans-Joachim Krause1,
Alex I. Braginski2, Andreas Offenhäusser2; and Mianheng Jiang1

e-mail: [email protected]

1State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050, People’s Republic of China
2Institute of Bio- and Nanosystems (IBN-2), Forschungszentrum Jülich,
D-52425 Jülich, Germany
3Institut für Angewandte Physik, Justus-Liebig-Universität Gießen,
D-35392 Gießen, Germany

Abstract - We present a new dc Superconducting QUantum Interference Device (SQUID) readout circuit operating in the voltage bias mode and called SQUID Bootstrap Circuit (SBC). The SBC consists of two parallel branches: the first one consists of a dc SQUID with an inductively coupled feedback coil; it is used for the enhancement of the flux-to-current coefficient. The second branch consisting of a shunt resistor and a coil inductively coupled to SQUID suppresses the preamplifier noise current by increasing the dynamic resistance. Consequently, the SBC effectively reduces the preamplifier noise below the SQUID intrinsic noise. For helium-cooled planar SQUID magnetometer with a SQUID inductance of 350 pH, flux noise of about 4 µΦ0/Hz and magnetic field resolution of 3 fT/ Hz, were obtained. The SBC leads to a simple and convenient readout electronics for dc SQUID.

Keywords - SQUID, direct readout, low noise electronics

Submitted January 14, 2010; accepted January 18, 2010. Reference No. ST184; Category 4.
On January 11, 2010, this paper was published in SuST: Supercond. Sci. Technol. 23 065016 (2010).