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LMV834 / for audio application

K.Yaita
Guru 29635 points
Other Parts Discussed in Thread: LMV834, LMV854, LMV862, OPA376

Hi Team,

My customer considers to use LMV834(4channel) for high-pass filter and for amplification of analog microphone line(L&R).
He would like to know if there is track record to use LMV83x for audio application.
Could I get any information for this requirement?

Best Regards,
Yaita

  • 0
    TI__Mastermind 46196 points
    Hello Kensuke,

    The original definition for this family was inspired by a microphone amp to reduce the effect of EMI on microphone liens.

    It is targeted to portable applications, so there is a tradeoff between noise and supply current. While not "audiophile" specs (OPA16xx series), it has respectable noise, power, output drive and bandwidth for audio. If you need more BW, see the LMV854 or LMV862 (no quad).

    A major manufacturer of webcams uses this device family to reduce the effect of EMI (cellphone) pickup on their microphones.

    Regards,
  • 0 in reply to Paul Grohe
    Guru 29635 points

    Hi Paul-san,

    Thank you for your valuable informtion!
    It is helpful for my customer.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29635 points

    Hi Paul-san,

    Thanks to your advice, my customer took LMV834 on his audio board.
    I really appreciate for your support!

    I would like to have your advice again.

    My customer currently uses LMV834 for amplification of analog microphone line and he considers to change it's single-end output to differential output for next model of his application.
    He would like to adopt the diffferential cable in terms of noise performance.
    Is there any solution that he still uses LMV834?

    He also considers to use fully differencial OPamps but it seems to be more expensive.

    Best Regards,
    Yaita / Japan disty

  • 0 in reply to K.Yaita
    TI__Mastermind 46196 points
    Hi Kensuke-san,

    Yes. The LMV834 can be used in a differential drive.

    There is a nice differential electret microphone circuit in Figure 30 of the OPA376 datasheet. The LMV834 should also work fine in that circuit (while adding EMI protection). Everything on the left up to the 33uF caps is the differential mic driver circuit.

    As a side note - If EMI protection is part of the requirement, make sure the microphone element also has internal EMI filtering. If the noise gets into the microphone, no amount of filtering on the amplifier side will eliminate the noise.

    Regards,
  • 0 in reply to Paul Grohe
    Guru 29635 points

    Hi Paul-san,

    Thank you for your advice!
    I informed the circuit to my cutomer.

    I would also like to ask the following.
    If the output of audio codec is differential signal, do you recommend fully differential amplifier?
    Is there LMV834 solution for this case too?




    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29635 points

    Paul-san,

    I appreciate if you have an advice. 

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29635 points

    May I have your advice?
    If you need more information, please let me know.

    Best Regards,
    Yaita