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DC Gain Linearity Error of LME49724

Gabriel Brunheira
Intellectual 440 points
Other Parts Discussed in Thread: LME49724, LME49860, LM4562

Hi everyone,

What exactly does the DC Gain Linearity Error specified in the first page of LME49724 datasheet mean? What were the operation conditions, for which this parameter was measured? Would you recommend this part for a high DC precision application?

Thanks in advance!


Gabriel

  • 0
    TI__Guru**** 189399 points

    Hi, Gabriel,

    Unfortunately, I do not have further information about this parameter.

    While this device might be a good choice for your application, we have an entire catalog of high precision op amps. You might want to check some of those as well.

    -d2

  • 0 in reply to Don Dapkus
    Intellectual 440 points

    Hi Don,

    Thanks for the attention, but I really couldn't understand what you mean with you answer. Doesn't TI have any information about this parameter at all, even though it is present in many other datasheets (LME49710, LM4562, LME49860)?

    I've already looked for solutions in the high precision section, but I couldn't find any parts .

    My circuit is a fully-differential antialiasing filter (diff in/diff out), which has a +/-10 V input range, with Gain = 2. It is the signal conditioner circuit for an 18-bit ADC, with +/- 20V differential input.

    There are few fully-differential-amplifiers on the market, which can operate under this conditions. The TI THS41** family is one of them, but most of specifications from LME49724 are much better than from this family (and of course, the price). Even the DC parameters are better, although this is specified for audio applications.

    In my measurements, I'm getting a maximum non-linearity of 60 ppm (~15 LSB from my 18-bit ADC) between input and output.

    The PCB layout was made according the Thermal Pad recommendations, and the IC maximum temperature was below 50ºC, with a deviation of 5ºC within the input range. So I think it isn't a temperature problem.

    Then I've started to think it could be the effect of nonlinearity of the Open Loop DC Gain from LME49724, but there isn't any information about it, except this one I've asked for. I couldn't find any method to measure it by my self (I only found for single-ended circuits).

    My feedback resistors may dissipate up to 66 mW, but I don't think it would be enough to warm it up and change the closed-loop gain.

    Do you have any suggestions?

    Thanks again!


    Gabriel