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LME49710, LME49720 and LME49860 Differential Input Diodes

Wayne Kirkwood
Intellectual 415 points
Other Parts Discussed in Thread: LME49720, NE5534, NE5532, LME49860, MC33078, TL072, OPA1612

Hi everyone -


I'm posting to seek confirmation that the LME49710, LME49720 and LME49860 all have differential back-to-back protection diodes from the non-inverting to inverting inputs similar to an NE5532/NE5534.

I realize that the datasheet states that the inputs are limited to "(V-) - 0.7V to (V+) + 0.7V. That question is already addressed here:

http://e2e.ti.com/support/amplifiers/audio_amplifiers/f/6/p/250380/880808.aspx#880808

However, from tests it appears that there are also diodes differentially-connected to limit the differential input to +/- 0.7V. In audio applications this is usually of no consequence with the inputs held in null by feedback, but in applications such as a precision audio DC clamp (e.g. an audio DC-restore circuit) or comparator applications (admittedly not a good choice for the LME49710) this prevents some common op amp applications.

As previously mentioned the NE5532/5534 have these diodes, two common op amps that don't, the TL072 and MC33078 do not.

If these diodes are present in the LME49710, LME49720 and LME49860 (all excellent parts BTW) maybe the datasheet should tell us that they're in there as it does in the NE5532/5534.

  • 0
    TI__Guru**** 189399 points

    Hi, Wayne,

    Thanks for your thorough analysis of the problem, and the feedback!

    I don't anticipate updating these data sheets soon, but I will log this in our system to fix the next time we do revise them.

    We are trying to grow a vibrant audio community here, but we have not been very successful so far. I encourage you, and others like you, to share you knowledge and experience in the audio field with others. Inside TI, we don't always understand how our customers use our parts, and having a voice from the other side of the fence is very helpful!

    So, please surf around, and add comments where you feel you can.

    -d2

  • 0 in reply to Don Dapkus
    Intellectual 415 points

    Thanks Don. I see that I'm 137,900 points behind you so I'll do my best to visit more often.


    The LME49710, 49720 and LME49860 are my "go to" parts now for bipolar input audio op amps in 30 and 36V applications.

  • 0 in reply to Wayne Kirkwood
    Prodigy 10 points
    Your LME series of opamps are truly spectacular. Lots of us are using them, trust me.
  • 0 in reply to Don Dapkus
    Prodigy 40 points

    Hi,

    I wonder what TI is doing with the "LMExxx" family of ICs.  I can't get a straight answer from TI customer support and many of these parts are no longer listed in the "Audio" or "Precision " sections of the web site.  Specifically I asked about the longevity and availability of the LME49860.  While only one version (LME49860MAX/NOPB) is shown as "Active", there are none in existence for the last > 2 months anywhere, including TI & all Distros.  This dual OpAmp has great performance including: +/-22V operating V, behaves well with capacitive loads,  and can drive 600 Ohm Loads all day at ~40 Vp-p while meeting spec.  Nothing from BB makes can do this, even though the OPA1612 has 1/2 the THD specs and lower noise.

    It almost seems that TI is going with all the BB parts for Audio, and phasing out the National parts. What's up?

    Imre Csaszar