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Another electret Q

Discussion in 'Electronic Basics' started by phil, Apr 29, 2004.

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  1. phil

    phil Guest

    What about a configuration such as this one here
    http://www.uoguelph.ca/~antoon/circ/fmt2.htm


    We know that the base of the transistor settles on 0.7V.
    Does this mean that the microphone will only have 0.7V,
    they usually need more than that, don't they?
     
  2. grahamk

    grahamk Guest

    The base voltage is about 0.7 volts higher than the emitter volts.
    If the emitter is 2 volts then the base is 2.7 volts.
     
  3. phil

    phil Guest

    This is true, the problem is that electrets vary considerably
    in dc current. For example, some would use 0.5mA, others
    would use 5mA. There does not seem to be any way to
    determine what voltage is going to be at the emitter.



    The base voltage is about 0.7 volts higher than the emitter volts.
    If the emitter is 2 volts then the base is 2.7 volts.
     
  4. Ian Bell

    Ian Bell Guest


    Quite right. Now you know why this is a poor design.

    Ian
     
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