This title appears in the Scientific Report :
2015
Please use the identifier:
http://dx.doi.org/10.1016/j.physc.2015.03.009 in citations.
Practical dc SQUID system: Devices and electronics
Practical dc SQUID system: Devices and electronics
In order to set up a liquid helium-cooled practical dc SQUID system with acceptable noise figure, we employ a weakly damped dc SQUID with a large flux-to-voltage transfer coefficient ∂V/∂Ф in a direct readout scheme (DRS) without flux modulation. Two preamplifiers are utilized: (1) AD 797 for a so-c...
Saved in:
Personal Name(s): | Zhang, Guofeng |
---|---|
Zhang, Yi (Corresponding author) / Hong, Tao / Wang, Hai / Krause, Hans-Joachim / Xie, Xiaoming | |
Contributing Institute: |
JARA-FIT; JARA-FIT Bioelektronik; PGI-8 |
Published in: | Physica / C, 518 (2015) S. 73 - 76 |
Imprint: |
Amsterdam
North-Holland Physics Publ.
2015
|
DOI: |
10.1016/j.physc.2015.03.009 |
Document Type: |
Journal Article |
Research Program: |
Controlling Configuration-Based Phenomena |
Publikationsportal JuSER |
In order to set up a liquid helium-cooled practical dc SQUID system with acceptable noise figure, we employ a weakly damped dc SQUID with a large flux-to-voltage transfer coefficient ∂V/∂Ф in a direct readout scheme (DRS) without flux modulation. Two preamplifiers are utilized: (1) AD 797 for a so-called “single chip readout electronics” (SCRE); (2) 6 parallel-connected bipolar transistors (PCBT). The latter reduces the preamplifier voltage noise Vn but increases its current noise In, which plays a leading role in the system low-frequency noise. We introduce a current feedback circuit (CFC) consisting of an inductor Li coupled to the SQUID with mutual inductance Mi to improve the noise performance. In this work, the preamplifier In contribution and CFC are analyzed. To evaluate the In suppression with CFC, two criteria are presented. Furthermore, we establish a dimensionless parameter ξ to describe CFC quantitatively. The system noise is compared with and without CFC using the two preamplifiers. For a dc SQUID with a loop inductance of 350 pH, an intrinsic noise of about 5 μФ0/√Hz and a corner frequency at 2 Hz are measured using PCBT with CFC. |