DC-SQUID electronics based on adaptive noise cancellation and a high open-loop gain controller

Heikki Seppä

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review


    A low-noise SQUID readout electronics with a high slew rate and an automatic gain control feature has been developed. Flux noise levels of 5×10−7Φ0/√Hz at 1 kHz and 2×10−6Φ0/√Hz at 1 Hz have been measured with this readout scheme. The system tolerates sinusoidal disturbances having amplitudes up to 140 φ0 at 1 kHz without loosing lock. The electronics utilizes a cooled GaAs FET to control the cancellation of the voltage noise of the room temperature amplifier, a PI 3/2 controller to provide a high open-loop gain at low frequencies, and a square-wave flux and offset voltage modulation to enable automatic control of the noise reduction. The cutoff frequency of the flux-locked-loop is 300 kHz and the feedback gain is more than 130 dB at 10 Hz.
    Original languageEnglish
    Title of host publicationSuperconducting Devices and Their Applications
    EditorsHans Koch, Heinz Lübbig
    Place of PublicationHeidelberg
    ISBN (Electronic)978-3-642-77457-7
    ISBN (Print)978-3-642-77459-1
    Publication statusPublished - 1992
    MoE publication typeA4 Article in a conference publication
    Event4th International Conference SQUID ’91 - Berlin, Germany
    Duration: 18 Jun 199221 Jun 1992


    Conference4th International Conference SQUID ’91


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