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Asymmetric supply

Eric Belarbre
Prodigy 30 points
Other Parts Discussed in Thread: LM7121, LMH6723, OPA890, THS4221, THS4222, SN10501

Dear community,

I struggle to find the right amplifier for my application, mainly because it requires a high voltage (>11V) and a perfect 0V (negative supply needed).

The main specs are :

  • Unity gain stable
  • Slew rate > 500 V/us
  • Alim positive > 12 V
  • Alim negative < -1 V 
  • Swing min. +11.5V

If the symmetrical supply is necessary, the LM7121 is almost good, but not enough.

If we can use a -1V / 12V supply, the OPA890 or the LMH6723 are much better and much cheaper.

The footprint also depends on this strategy.

Is there any specific amplifier which can handle -1V / +12V supplies ?

Thanks in advance.

  • 0
    TI__Genius 12631 points

    Eric,

    I think the THS4221 may be a good choice for your requirements. Please let me know if something is missing and I can try to see if there is a better match.

    -Samir

  • 0 in reply to Samir Cherian
    Prodigy 30 points

    Any ways to know if it'd be working with a -2V / 12V supply ? 

    The simulation works, but it always does (with -2/+13 actually, because the swing of the THS4221 is not that good).

    The price is near 2$ for it, but only 1.38$ for the THS4222. The same amplifier is cheaper when dual ...

    If the asymmetric supply is an option, then there are plenty amplifier which can have these specs and that are cheaper than 1$ ... how bad is it to shift the rails ?

    Thanks for the reference, Samir.

    Eric

  • 0 in reply to Eric Belarbre
    TI__Genius 12631 points
    Eric,
    All amplifiers can work on asymmetric rails. One only has to make sure that the common-mode requirements of the amplifier are satisfied.

    The THS4221 can work with -2/+13V supplies as that is within the specified total supply range of 15V.
    -Samir
  • 0 in reply to Samir Cherian
    Prodigy 30 points

    Ok it simplifies everything, any amplifier with a 15V max can work.

    With a good swing, maybe some 12V max could be fine too.

    To be able to test a few of them, I'll focus on the SOT-23 footprint. I found the SN10501 which should do the job.

    Do you know of any other good amplifier ? 

    Anyways, thank you for the help,

    Eric

  • 0 in reply to Eric Belarbre
    TI__Genius 12631 points
    Hello Eric,
    For the SOT-23 footprint it looks like your closest matches are the SN10501 and THS4221. I will also contact our marketing team to figure out why the price on the THS4221 is more than the THS4222.
    -Samir