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IEEE Electron Device Letters

100 GHz Binary counter based on DC SQUID's

C.A. Hamilton, Frances L. Lloyd

Published Nov 1, 1982• 64 citations
Publisher

Abstract

A binary counter using bistable dc SQUID's as flip flop circuits is demonstrated. All of the functions: LOAD, COUNT, STORE, READ, and CLEAR can be performed. The use of single flux quantum logic results in high sensitivity (10-18J input pulse energy), high speed (100 GHz count rate) and low power (10-7W at 100 GHz count rate).
DOI
10.1109/edl.1982.25592

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High speed, single flux quantum (SFQ) binary scalers are important components in superconducting analog-to-digital converters (ADC). This paper reviews the concept for a SQUID ADC and the design of an SFQ binary ripple counter, and reports the simulation of key components, and fabrication and performance of non-latching SQUID scalers and SFQ binary ripple counters. The SQUIDs were fabricated with Nb/Nb2O5/PbIn junctions and interconnected by monolithic-superconducting transmission lines and isolation resistors. Each SQUID functioned as a bistable flip-flop with the input connected to the center of the device and the output across one junction. All junctions were critically damped to optimize the pulse response. Operation was verified by observing the do I-V curves of successive SQUIDs driven by a cw pulse train generated on the same chip. Each SQUID exhibited constant-voltage current steps at 1/2 the voltage of the preceding device as expected from the Josephson voltage-to-frequency relation. Steps were observed only for the same voltage polarity of successive devices and for proper phase bias of the SQUID. Binary frequency division was recorded up to 40GHz for devices designed to operate to 28GHz.