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  • Has anybody tried this transimpedance amplifier?

    From Jean-Pierre Coulon@21:1/5 to All on Thu Nov 16 16:26:52 2023
    https://www.newport.com/p/70710.

    Is the input current noise lower than that of the LT1028 below 1 kHz?

    Regards,
    --
    Jean-Pierre Coulon

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  • From John Larkin@21:1/5 to coulon@cacas.pam.oca.eu on Thu Nov 16 09:00:59 2023
    On Thu, 16 Nov 2023 16:26:52 +0100, Jean-Pierre Coulon <coulon@cacas.pam.oca.eu> wrote:

    https://www.newport.com/p/70710.

    Is the input current noise lower than that of the LT1028 below 1 kHz?

    Regards,

    You can buy opamps with noise less than 1 fA/rthz.

    LT1028 is bipolar, 1000x that noise.

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  • From Jean-Pierre Coulon@21:1/5 to John Larkin on Thu Nov 16 21:45:20 2023
    On Thu, 16 Nov 2023, John Larkin wrote:

    You can buy opamps with noise less than 1 fA/rthz.

    The AD549 has a promising current noise. I must experiment because of is undocumented voltage noise at the frequencies I want.

    --
    Jean-Pierre Coulon

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  • From Phil Hobbs@21:1/5 to Jean-Pierre Coulon on Thu Nov 16 16:37:58 2023
    On 2023-11-16 15:45, Jean-Pierre Coulon wrote:
    On Thu, 16 Nov 2023, John Larkin wrote:

    You can buy opamps with noise less than 1 fA/rthz.

    The AD549 has a promising current noise. I must experiment because of is undocumented voltage noise at the frequencies I want.


    If you post a bit more about what you're actually trying to measure, we
    can probably be more help.

    A TIA with 4 pA/sqrt(Hz) noise, 100 kHz bandwidth, and 10**9 ohms transimpedance will have an output noise floor of

    E_N ~ 4e-12*1e9*sqrt(1e5 * pi/2) = 1.6 Vrms.

    [The pi/2 is the ratio of the noise bandwidth of a 1-pole rolloff
    (1/4RC) to its 3-dB bandwidth (1/2piRC).]

    Viewed on an oscilloscope, that'll look like a 6-V wide stripe down the
    middle of the display, with outliers up to +-5V at least.

    Not exactly your state-of-the art low noise amplifier!

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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