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  • 1
    Electronic Resource
    Electronic Resource
    Low-noise preamplifier with input and feedback transformers for low source resistance sensors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2089-2094 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design, schematics, and performances of a very-low-noise, low-frequency preamplifier. It operates in the 5 Hz–100 kHz range and offers an input equivalent voltage noise density as low as 65 pV/(square root of)Hz; the current noise increases with frequency and settles to about 1.5 pA/(square root of)Hz at 100 kHz. The amplifier uses input and feedback signal transformers and operates in full differential mode; a −163 dB common-mode rejection ratio is achieved at line frequency. Design methodology is applicable to other ranges of frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143171
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  • 2
    Electronic Resource
    Electronic Resource
    A formal presentation and comparative study of low-frequency noise reduction techniques for direct current superconducting quantum interference devices (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 796-804 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a comparative study of existing low-frequency noise reduction techniques for dc superconducting quantum interference devices (SQUIDS). These methods are essential to applications involving high-Tc SQUIDS because they dramatically reduce the 1/f noise to useful low-frequency noise levels. We propose a formal presentation of the problem and explain mathematically the working principles of these noise reductions methods, particularly for fluctuations arising from the critical current of the junctions. An increase in the white noise level is generally observed when a sinusoidal lock-in detection is used for these methods and we give here a mathematical explanation for this peculiar effect. Finally, noise measurements made on high-Tc grain boundary dc SQUIDS are presented; the experimental results are in close agreement with theory. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146812
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Superconducting fast microbolometers operating below their critical temperature (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3858-3868 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bolometric nature of the optical sensitivity of YBCO (YBa2Cu3O7−δ) thin-film microstrips in the superconducting state is demonstrated. Below the critical temperature Tc the critical current temperature dependence of the device provides a suitable temperature sensor. A theoretical thermal model that gives reliable forecasts for the sensor time constant and sensitivity over the 10–90 K temperature range has been developed. Sensitivity measurements on high-quality YBCO films deposited on MgO are in quite good agreement with the model, showing that the observed signals are entirely bolometric. The effective heat capacity of the sensor is that of the film in the irradiated area. Owing to the high thermal conductivity of MgO, the substrate stays at the heat sink temperature and the main resistance to heat flow is the film/substrate interface. The heat capacity of the irradiated area of the film, strongly coupled to the heat sink through the thermal boundary resistance gives high-speed bolometers behaving as first-order systems. For SrTiO3 or ZrO2 substrates, their lower thermal conductivity would lead to higher time constants and more complicated behaviors. The precise origin of the measured sensor noise has still to be established. On a 0.2×10×15 μm3 microbridge at 85 K (below the critical temperature), a noise equivalent power of 120 pW/(square root of)Hz and a time constant τ of 20 ns were measured; this corresponds to a noise equivalent temperature of 60 nK/(square root of)Hz and a specific detectivity D* of 1.8×106 cm (square root of)Hz/W. A more relevant criterion for comparing optical sensors is the D*/(square root of)τ ratio. In the case presented, this ratio is equal to 1.3×1011 cm/J which is one of the best values published at this time. Such performances should give competitive composite or antenna coupled bolometers compared to existing sensors for wavelengths greater than 20 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357390
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    Paper (German National Licenses)
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