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Design and Operation of HTS SFQ Circuit Elements
Koji TSUBONE Hironori WAKANA Yoshinobu TARUTANI Seiji ADACHI Yoshihiro ISHIMARU Keiichi TANABE
Publication
IEICE TRANSACTIONS on Electronics
Vol.E90-C
No.3
pp.570-578 Publication Date: 2007/03/01 Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.3.570 Print ISSN: 0916-8516 Type of Manuscript: Special Section INVITED PAPER (Special Section on Innovative Superconducting Devices and Their Applications) Category: Keyword: single flux quantum (SFQ) circuit, ramp-edge junction technology, toggle flip-flop, thermal noise, high-temperature superconductor,
Full Text: PDF(1.4MB)>>
Summary:
Single flux quantum (SFQ) circuit elements have been designed and fabricated using the YBa2Cu3O7-δ ramp-edge junction technology. Logic operations of SFQ circuit elements, such as a toggle flip-flop (T-FF), a set-reset flip-flop (RS-FF), and a 96-junction Josephson transmission line (JTL), were successfully demonstrated, and dc supply current margins were confirmed up to temperatures higher than 30 K. The circuit layout was improved in order to suppress the critical current (Ic) spread that appears during the junction fabrication procedure. By employing the new circuit layout rule, correct operations at temperatures from 27 K to 34 K with dc supply current margins wider than 7% were confirmed for the T-FF with a single output. Moreover, the maximum operating frequencies of T-FFs were measured to be 360 GHz at 4.2 K and 210 GHz at 41 K, which are substantially higher than the values for the circuits with the conventional layout. According to the simulation result, the maximum operating frequency at 40 K was expected to be approximately 50% of the characteristic frequency at a bit error rate (BER) less than 10-6.
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