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Amplifying a analog microphone signal to be read for a data acquisition device

Richard Deppisch

Other Parts Discussed in Thread: PGA2500, LME49990

Hello,

This is my first official post, but I have browsing your forum for awhile to troubleshoot my other problems. I wanted to ask the community what it recommends that I do to boost a simple 3pin 3.5mm microphone signal so that it can be viewed with a data acquisition device. I am assuming a in line amplifier would work and I am currently testing that theory, but I wanted to ask the opinion of the community on how to go about doing this.

Thanks

  • 0
    TI__Expert 3840 points

    Hi Richard,

    There are generally a number of variables to consider, namely signal level available and desired (ie gain required), signal frequency, power supply voltages desired, cable length to the amplifier. To start with, you can use any low-noise amplifier; an LME49990 would be more of a high-end preamp, while the PGA2500 is an industry standard preamp with more control. For long cable lengths an instrumentation amp would also be useful for common-mode rejection. A few places to start.

    Best Regards,

    JD

  • 0 in reply to John De Celles

    I am actually already using several premade circuits to try and boost my signal. They are supposed to boost the signal 40 db but for some reason, the microphone is still not showing any activity. I am trying to produce a relatively low noise signal, power supply does not matter for the most part, and the desired level does not matter as long as the signal shows when a sound is recorded.

  • 0 in reply to Richard Deppisch
    TI__Expert 3840 points

    Hi Richard,

    Have you verified that your present amplifier is giving you the gain of 40dB as expected? Using a signal generator to validate your pre-amp first, will take the connections and operation of the microphone out of the equation.

    Microphone signals could be in the uV level, so only 40dB of gain may not be enough; you may need to add another stage to get the level where you expect it.

    Best Regards,

    JD

  • 0 in reply to John De Celles

    I think the last part you said about 40dB not being enough is true. I actually put two of them in line with each other and now the signal is maxing out the DAQ, but I can tell when there is activity. It is very noisy, but it is activity.

    I think the signal is in micro-volts which would explain a lot.

    I realize that two 40dB in series multiply the gain, so I was wondering what route you think I should go with from here? I am using a 12V power supply.

    Should I combine two different and smaller amplifiers or go with one lone amplifier? I figure a 40db and maybe a 10 might work. Ideally I would be able to control the db without having to change the voltage though.


    So any recommendations on where I should go from here?