Some phenomena due to SQUID input properties when local feedback is present

Mikko Kiviranta (Corresponding Author), Leif Grönberg, Nikolay Beev, J van der Kuur

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    9 Citations (Scopus)


    We have constructed a two-stage SQUID amplifier, in which series-mixing local feedback has been used to screen the SQUID input inductances and hence to boost the power gain of the amplifier. 2.9 pA/Hz1/2 current noise and 2.9 nH input inductance of the lower SQUID stage imply energy resolution of 18 times Planck constant at 4.2 K, which, arguably, can be further improved by input inductance screening. The upper stage consists of a 184-series 4-parallel SQUID array, which, when used alone, shows lower than 0.03 µF 0/Hz1/2 flux noise, but which as a part of the two-stage amplifier is operated at a higher flux noise level to provide robust, EMI-tolerant output signal. The series-mixing feedback also facilitates negative SQUID input impedance, which would allow self-oscillating SQUID-based frequency domain multiplexing
    Original languageEnglish
    Article number042017
    JournalJournal of Physics: Conference Series
    Issue numberPart 4
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed
    Event11th European Conference on Applied Superconductivity, EUCAS 2013 - Genoa, Italy
    Duration: 15 Sep 201319 Sep 2013
    Conference number: 11


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