microphone pre-amp, op-amp

Discussion in 'General Electronics Chat' started by bug13, Sep 22, 2014.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Hi guys

    I am looking into making a simple microphone pre-amp, I will just need a gain of about 10. When I looked at the circuit from the datasheet (LME49726). The datasheet shows us using inverting configuration. And same as most of the other circuit I looked at.

    My question is: why using an inverting configuration? why not a noninverting configuration? What is the advantage of using a inverting configuration?

    thanks guys!
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Mono Preamp

    The reason I chose this configuration is fixed impedance.
     
  3. #12

    Expert

    Nov 30, 2010
    16,337
    6,821
    Look at your datasheet for figures: 29, 32, 33,38,39,46,47, and 48.
    What is the advantage of using a non-inverting configuration?
    Why do you think there is an advantage to one configuration instead of the other?
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,042
    3,243
    A big advantage of a non-inverting configuration is that it has a high input impedance, equal to the impedance of the op amp input terminal. An inverting amp configuration has an input impedance equal to whatever the selected input resistor is which is generally much lower. A non-inverting configuration also has a higher bandwidth as compared to the inverting configuration with the same gain.

    The biggest advantage of an inverting configuration is that the minus input node acts as a virtual-ground summing junction so it's easy to add extra input resistors in parallel to allow near ideal summing of different signals. A non-inverting configuration has interaction between multiple inputs, so summing signals is not as simple.
     
    Sensacell likes this.
  5. #12

    Expert

    Nov 30, 2010
    16,337
    6,821
    So you see, each circuit has its "advantages", but the way to decide what an advantage is requires knowing what the circuit needs.

    Personally, I prefer the non-inverting for this job because I can set the input impedance anywhere I like, add frequency filters before this very high input impedance, and adjust the gain on the inverting side while causing no interference with the input signal, or add more frequency filters in the negative feedback loop.

    If I had to combine 2 signals, that logic would be useless and I would want an inverting configuration.

    The definition of advantage depends on what you need today.
     
    bug13 likes this.
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