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Measurement bandwidth for Nationals Ultra-Low Distortion Op-Amps (LME49990, LME49724 and LM4562).

DMM
Intellectual 290 points
Other Parts Discussed in Thread: OPA1612, LME49990, OPA1632, LME49724, LM4562

Hi:

I was looking at the datasheet for the LME49990, LME49724 and LM4562 and didn't see anywhere in the datasheets what the measurement bandwidths were for the low distortion numbers claimed in the datasheets. It is listed for the TI part (OPA1632 and OPA1612) but not for the former National parts.

Also the gain/phase plots are missing as well...

I want to compare the two parts (TI and former National) and decide which is best for my application.

Thanks,

David

  • 0
    TI__Guru 52115 points
    Hi David,

    Let me double check with my colleague to see whether we have the right data for you.

    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Guru 52115 points
    Hi David,

    I have contacted my colleague for these gain/phase plots. The gain/phase plot for LM4562 does exist in its datasheet (See Figure 106). However, no plots for LM49990 and LME49724.

    As for the measurement bandwidths, we don't have the answers either. However, I think you can guess based on the GBWP and Av in their datasheets. Note that unity gain frequency and GBWP is not always the same. For example, LM4562's GBWP is 55MHz but in the gain/phase plot the unity gain frequency is around 30MHz.

    Andy
  • 0 in reply to Andy Liu (BMS)
    Intellectual 290 points

    Andy:

    Thank you for your response but I'm really disappointed that the tests conditions under which the (former) National parts are no longer available. Normally, audio distortion measurements are done using a 22Hz - 20kHz bandwidth or an 80kHz bandwidth of the AP audio test system. Your OPA16xx series even lists distortion specs using bandwidths up to 500kHz using the same AP system.

    So how am I supposed to compare the OPA1612 to the LM4562? Or the LME49724 to the OPA1632 differential opamp as far as their distortion characteristics are concerned? Were the LM(E) parts measured using a 20Khz BW or an 80kHz BW?

    David

  • 0 in reply to DMM
    TI__Guru 52115 points

    Hi David,

    LM4562 and LME49724 are legacy audio devices originally designed by National Semiconductor. I am not very sure whether we still can find the raw data but I will try my best.

    Andy

  • 0 in reply to Andy Liu (BMS)
    Intellectual 290 points

    Andy:

    I really appreciate your efforts and thank you for that. I wasn't aware these were products. Does it mean they will be discontinued soon or simply you inherited them from National and have no access to the original engineers and their data?

    What are their replacements of equal performance? Would they be the SoundPlus OPA161x and OPA1632 series of amplifier?

    Also how accurate are the simulation models for these legacy National parts in TINA? More or less accurate than the sim models for the SoundPlus parts?

    Lots of questions, I know and hope you answer each one of them.

    Thanks,

    David

  • 0 in reply to DMM
    TI__Guru 52115 points

    Hi David,

    See my comments below:

    a) Does it mean they will be discontinued soon or simply you inherited them from National and have no access to the original engineers and their data?

    As far as I am concerned, both LM4562 and LME49724 will stay alive for a long time because our customers are still quite interested in these 2 devices due to their excellent performance. They are legacy devices from NS but we will continue to support them as much as we can.

    b) What are their replacements of equal performance? Would they be the SoundPlus OPA161x and OPA1632 series of amplifier?

    I think OPA161x and OPA1632 are very good options as well.  Personally I would recommend them since we can provide better support for them than LM4562 and LME49724.

    c) Also how accurate are the simulation models for these legacy National parts in TINA? More or less accurate than the sim models for the SoundPlus parts?

    I don't know the answer, but I will suggest you try the sim models of the SoundPlus parts first. 

    Andy