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What is the noise factor of ad8338?

  • Hi rookie1,

    The Noise Factor will depend on the source impedance and also on the gain setting used. Here is an example calculation for AD8338 at maximum gain:

    F= 1 + Na / (Ni * G)

    Na = Output referred noise power (amplifier related)

    G = Power Gain

    Ni = Input noise power

    Assuming Vgain = 1.1V --> 80dB voltage gain (Node Pin High) --> output referred noise = 45,000nV/RtHz --> Na = 2.03e-9 V^2/Hz

    Assuming a source resistance of 50ohm --> Ni = (0.91nV/RtHz)^2 = 8.28e-19 V^2/Hz

    G = (10,000) ^2 = 1e8 V^2/V^2

    F = 1 + 2.03e-9 / (8.28e-19 * 1e8) = 25.4

    NF = 10*log(25.4) = 14.1dB

    Assuming I've not made any mistakes along the way!

    You can do your calculation based on the actual gain and input / source resistance accordingly.



  • Hi,

    Your answer is very helpful. I have one more question. Could you please tell me how to connect VAGC pin without using AGC feature of AD8338?

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