Presentation 2012-07-19
Design of Circuits Controlling Dependence of Signal Propagation Time on Bias Voltage for Expanding the Operating Margin of SFQ Circuits
Mikio OTSUBO, Yuki YAMANASHI, Nobuyuki YOSHIKAWA,
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Abstract(in English) Superconductive single flux quantum (SFQ) digital circuits can operate at a clock frequency of several tens GHz. However, the operating margin of the SFQ digital circuit decreases with increase of the operating frequency because timing error occurs at low bias voltage. In this study, a novel design method, which enables us to obtain wide operating margin at high operating frequency, has been investigated. In the proposed design method, timing error can be avoided by controlling dependences of signal propagation delay of Josephson transmission lines (JTLs) on the bias voltage. The proposed JTLs to control the dependence of propagation delay on the bias voltage has extra bias feeding line in addition to conventional bias feeding lines of the conventional JTLs. By adjusting resistance of the bias resistors in the extra bias feeding lines and the critical current of the Josephson junctions, the dependence of propagation delay on the bias voltage can be arbitrarily adjusted and we can avoid timing error occurs at low bias region. In measuring characteristics of proposed circuits, dependence of signal transmission time on bias voltage of proposed circuits changed between 0.87 ps and -0.21 ps in comparison with normal transmission lines. Circuit simulation results indicate that bias margin of a full adder, designed assuming the 2.5 kA/cm^2 Nb process, can be improved by 20% compared to a conventional design at a frequency of 20 GHz by employing our novel design method.
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Keyword(in English) Single flux quantum circuits / Josephson transmission line / Timing error / Full adder
Paper # SCE2012-10
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Conference Information
Committee SCE
Conference Date 2012/7/12(1days)
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Registration To Superconductive Electronics (SCE)
Language JPN
Title (in Japanese) (See Japanese page)
Sub Title (in Japanese) (See Japanese page)
Title (in English) Design of Circuits Controlling Dependence of Signal Propagation Time on Bias Voltage for Expanding the Operating Margin of SFQ Circuits
Sub Title (in English)
Keyword(1) Single flux quantum circuits
Keyword(2) Josephson transmission line
Keyword(3) Timing error
Keyword(4) Full adder
1st Author's Name Mikio OTSUBO
1st Author's Affiliation Yokohama National University()
2nd Author's Name Yuki YAMANASHI
2nd Author's Affiliation Faculty of Engineering, Yokohama National University
3rd Author's Name Nobuyuki YOSHIKAWA
3rd Author's Affiliation Faculty of Engineering, Yokohama National University
Date 2012-07-19
Paper # SCE2012-10
Volume (vol) vol.112
Number (no) 138
Page pp.pp.-
#Pages 5
Date of Issue