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OPA2348: Microphone circuit

Intellectual 360 points

Replies: 25

Views: 324

Part Number: OPA2348

Hi Sir,

Microphone specifications:  -35db (Sensitivity )  ,  60db(SNR)

Sound distance: 70db @ 6m

After going through the amplifier circuit, we want to get an output of about 300mV.

How much magnification do we need to design?
Do you have any recommended parts?

  • Hi Jason,

    provided that it is a typical microphone specifiction, then 0dB = 1V / Pa = 94dB(SPL). 70db(SPL) means 0.063Pa. And a sensitivty of -35dB results in a signal of 0.018V x 0.063 = 1.1mV at 70db(SPL). So, for 300mV output level you would need a total gain of about factor 270.

    To recommed a suited OPAmp we need to know what kind of microphone we are speaking about. Is it a dynamic microphone or an electret microphone? So, please give us more details on the microphone. Do you have a datasheet of microphone?

    Kai

  • In reply to kai klaas69:

    Thanks for the help Kai!

    Yes, Jason.  A part number and/or datasheet would definitely help here.  Let us know if there's any other information you may think is relative.

    Regards,

    Daniel

  • In reply to Daniel_Miller:

    Hi Kai,Daniel,

    Please refer to the following documents

    Thanks!

    WM-61A(A mic 規格書).pdf

  • In reply to Jason Li2:

    Hi Jason,

    you might want to have a look at this TI's reference design:

    tidu765.pdf

    Kai

  • In reply to Jason Li2:

    Hi Jason,

    The resource Kai has suggested is quite good and may be exactly what you need.  I don't have the correct font available in adobe to read your pdf, but from the image I'm guessing the microphone is an electret.

    As to selecting an amplifier, I think you should consider your power concerns and available supply rails.

    I'm not an expert on this subject, but having quickly gone through this design method I'm fairly confident we'll be able to find something to fit your needs.

    Regards,

    Daniel

  • In reply to Daniel_Miller:

    Hi Daniel,

    yes, it's an electret microphone:

    Kai

  • In reply to kai klaas69:

    Thanks Kai!

  • In reply to Daniel_Miller:

    Hi Kai,Daniel,

    <1>

    Is there a design using 3, .3v?

    If possible, we want to design low power consumption.

    <2>

    Which one do you recommend , inverting amplifier and  non-inverting amplifier?

    Thank you very much!

  • In reply to Jason Li2:

    Hi Jason,

    how much supply current would be acceptable?

    Kai

  • In reply to kai klaas69:

    Hi Kai,

    Because we need a total gain about factor 270. and bandwidth is 20KHz.
    I think we have two ways. Which one do you recommend? Or there is a better way?

    1. use 2 stage design: OPA2348(1MHz)
    iq=45uA x 2 =90uA
    2. use 1 stage design: TLV316(10MHz)
    iq=0.4mA


    <2>
    we saw that the document said:
    inverting amplifier is possible to achieve lower noise than with a non-inverting amplifier. But the R1 resistance must be higher than C3 impedance

    but if we use 3.3V power supply. R1 resistance can not be too large(about 2.2k)

    so should we use this design method? Or is there a better way?

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