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Replacement for fully differential AMP

Satoshi
Guru 19685 points

Other Parts Discussed in Thread: THS4531A, THS4130, THS4531

I looking for attached circuit of replace the LTC6350.

(±15Vinput ⇒ 0~3Voutput)

I have been a candidate for THS4531A, is it correct?

And, if there have more recommend device, please let me know.

Best regards,

Satoshi

  • 0
    Guru 19685 points
    Any update on this?

    I think that THS4130 is best, but customer hope more low cost solution.
    If THS4531A can use this specification, THS4531A is the best idea.

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Prodigy 300 points

    Hi Satoshi,

    The supply for the fully differential amplifier is 3V from the block diagram you attached.

    In that case THS4130 may not be suited since its minimum supply is 5V.

    THS4531A have similar performance of LT6350 at much reduced power.

    But flat band voltage noise of  THS4531A is 10nV/rtHz compared to 1.9nV/rtHz of LT6350.

    Can you let me know what is the resolution of the ADC which is being used and the frequency range?

    Thanks,

    Eldho

  • 0 in reply to Eldho George
    TI__Genius 12631 points

    Hi Eldho,

     Couple of things:

    1. The customer is using very large feedback and input resistors so that may become the dominant source. For example a 10k feedback resistor will result in 12.7nV/rtHz noise.

    2. The current noise of the LTC part is about 4 times higher than the THS4531, so 1pA/rTHz * 10k = 10nV/rtHz which is close to the voltage noise of the THS4531A.

    3. The amplifier is configured in a gain of 0.1V/V, so the voltage noise will actually be attenuated at the output and will not end up being a significant part of the final output noise.

    I think you should simulate this and provide a final noise number to Satoshi san.

    Satoshi-san,

    Can you please confirm if 100kOhm is the heaviest load that the previous stage can drive...or can it drive 10kOhm. Depending on how much the previous stage can drive we can suggest alternate architectures and ideas.

    -Samir