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preamp design for mic

Discussion in 'General Electronics Discussion' started by Kinshoro, Feb 18, 2010.

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  1. Kinshoro

    Kinshoro

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    Feb 18, 2010
    qqqqqqqqqqqqqqqqqqqqqqqq
     

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    Last edited: Apr 20, 2010
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I'd use AC coupling.

    If your 1.1V reference on the op-amp is out by even 30mV, the output will get pinned to one rail or the other.

    The chance that *something* isn't going to vary by a few mV is pretty slim. Your 1.1v reference is tied directly to your power supply and will vary with voltage, but worse, any noise on the supply rail will be amplified by your amplifier. (it would get amplified about 30 times)
     
  3. Kinshoro

    Kinshoro

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    Feb 18, 2010
    ac coupling

    Can u give me an example of a circuit with ac coupling and if possible with an inverting amplifier
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Do this then look at the top result.
     
  5. Kinshoro

    Kinshoro

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    Feb 18, 2010
    ac coupling

    I have a problem with the ac coupling... the value of capacitances are very high. plus when I ac couple the output terminal I get a waveform with 0v ref. Which gives me both negative and positive peaks. Could this damage my mic....
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What do you mean "the value of the capacitances are very high"?

    No, this will not damage your microphone, which is the *source* of the signal.

    You will probably have other problems (because you're using a single ended power supply) but this won't be one of them.

    Actually, the circuit I pointed you to is already designed for a single ended power supply.
     
    Last edited: Feb 20, 2010
  7. Kinshoro

    Kinshoro

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    Feb 18, 2010
    non inverting amplifier with ac coupling

    I have remodelled my design according to what you have told me... but the problem is now my opamp output is at a dc offset of 1.73V even though I am trying to keep it at a dc offset of 1.5 volts..... can anyone tell me how I can maintain the dc offset of my circuit....
     
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