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IEICE Technical Report; IEICE Tech. Rep.

Design and Operation of RSFQ Distributed Output Amplifier Equipped with double-stack SQUIDs

Komei Higuchi, Hiroshi Shimada, Yoshinao Mizugaki

Published Aug 2, 2019• 0 citations
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Component development for a 16 Gb/s RSFQ-CMOS interface system

Nobuyuki Yoshikawa, Toshio Abe, Yuichi Kato +1 more

We have been developing an RSFQ-CMOS interface system. The system consists of three modules: a 1 to 32 bit DDST demultiplexer which converts a 16 Gb/s SFQ data input into a 32-channel 500 Mb/s output, asynchronous stacked-SQUID amplifiers which amplify an SFQ data input into a 5 mV voltage level output, and 77 K CMOS amplifiers which amplify a 5 mV voltage level input into a 5 V output at 500 MHz. We have implemented the asynchronous stacked-SQUID amplifier and the 77 K CMOS amplifier using the HYPRES 1 kA/cm/sup 2/ Nb process and the ROHM 0.6 /spl mu/m CMOS process, respectively. It was demonstrated that the 24-stage asynchronous stacked-SQUID amplifier amplifies an SFQ data input into a 2.0 mV voltage level at 600 MHz. The 77 K CMOS amplifier was shown to amplify a 5 mV voltage level input into 5 V at 500 MHz from the simulation, and a 175 mV voltage input into 3.5 V at 90 MHz from the experiment.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•9 citations
We report the enhanced voltage swing of a rapid-single-flux-quantum (RSFQ) distributed amplifier by replacing a single superconducting quantum interference device (SQUID) with a double-stack-SQUID (DSS). A DSS is composed of two stacked 2-junction SQUIDs sharing one sensing inductor. Thanks to its stack structure, a DSS is expected to generate twofold output voltage. We have designed a 12-stage RSFQ distributed amplifier equipped with DSSs. The maximum output voltage swing reached 10.2 mV in simulation. Test chips were fabricated using a 25-µA/µm2 Nb integration process. In measurements, a test chip was cooled in a liquid helium bath. The experimental output voltage swing was up to 8.34 mV.
Recently, many groups have been developing on-chip Rapid Single-Flux-Quantum (RSFQ) output amplifiers which are designed to connect RSFQ circuitry to room temperature electronics. One of such amplifiers is a distributed SQUID amplifier comprising SQUIDs embedded in cascaded RSFQ RS flip-flops. In this paper, we propose a distributed double-SQUID amplifier, where a SQUID is replaced with a double-SQUID. Test circuit was fabricated using a niobium integration technology. Measurements were performed in a liquid helium bath. We confirmed that the maximum output voltage swing of a 4-stage distributed double- SQUID amplifier was 2.93 mV, which was comparable with the corresponding numerical value of 3.54 mV.
We have been developing an RSFQ-CMOS interface system. The system consists of three modules: a 1 to 32 bit DDST demultiplexer which converts a 16 Gb/s SFQ data input into a 32-channel 500 Mb/s output, asynchronous stacked-SQUID amplifiers which amplify an SFQ data input into a 5 mV voltage level output, and 77 K CMOS amplifiers which amplify a 5 mV voltage level input into a 5 V output at 500 MHz. We have implemented the asynchronous stacked-SQUID amplifier and the 77 K CMOS amplifier using the HYPRES 1 kA/cm/sup 2/ Nb process and the ROHM 0.6 /spl mu/m CMOS process, respectively. It was demonstrated that the 24-stage asynchronous stacked-SQUID amplifier amplifies an SFQ data input into a 2.0 mV voltage level at 600 MHz. The 77 K CMOS amplifier was shown to amplify a 5 mV voltage level input into 5 V at 500 MHz from the simulation, and a 175 mV voltage input into 3.5 V at 90 MHz from the experiment.