Connect with us

Max ratings of electret mic

Discussion in 'Electronic Basics' started by pimpom, Oct 23, 2008.

Scroll to continue with content
  1. pimpom

    pimpom Guest

    Can anyone please give me an idea of the maximum safe P.S.
    voltage of the ubiquitous cheap electret microphone used in
    portable recorders, cheap headphones-mic combos, lapel mikes,
    etc.? I mean those that have a built-in FET buffer/amplifier and
    are generally used with a P.S of 5V or less. TIA.
     
  2. Phil Allison

    Phil Allison Guest

    "pimpom"

    ** See: http://en.wikipedia.org/wiki/Electret_microphone

    See the schematic - it shows a resistor in series with the FET which MUST
    be there for it to work.

    The supply voltage can be anything from 1.5 volts up to 12 volts, depending
    on the particular capsule while the resistor can be from 2.2kohms up to
    10kohms.

    The voltage appearing across the FET will be half or less than the supply
    voltage.



    ...... Phil
     
  3. pimpom

    pimpom Guest

    Thanks for the reply. I understand the principles and I already
    looked up some catalogs, but none specified the max P.S. voltage.
    What I wanted to know was whether it would be safe (for the FET)
    to operate the microphone at something like 9-12V. I guessed it
    would be, but wanted confirmation.

    I expected that, like you said, the max ratings would differ for
    different models. But just as it would be unusual for a
    general-purpose low-power BJT to have a max Vce rating of less
    than 20V, I hoped that someone would be able to cite some voltage
    that could be expected to not exceed the max Vds rating of the
    vast majority of electret mikes.
     
  4. pimpom

    pimpom Guest

    Thanks for the reply. I understand the principles and I already
    looked up some catalogs, but none specified the max P.S. voltage.
    What I wanted to know was whether it would be safe (for the FET)
    to operate the microphone at something like 9-12V. I guessed it
    would be, but wanted confirmation.

    I expected that, like you said, the max ratings would differ for
    different models. But just as it would be unusual for a
    general-purpose low-power BJT to have a max Vce rating of less
    than 20V, I hoped that someone would be able to cite some voltage
    that could be expected to not exceed the max Vds rating of the
    vast majority of electret mikes.
     
  5. Phil Allison

    Phil Allison Guest

    "pimpom"

    ** Err - you just completely changed the nature of your question.

    P.S. voltage is one thing, max Vds of the FET is another.

    The whole point is that there IS a current limiting resistor - and if
    the PS voltage goes up, the SO must the value of that resistor.

    Plus - what the **** are you on about ????

    Your dopey Q simply has no context.

    Just like you.




    ...... Phil
     
  6. pimpom

    pimpom Guest

    Why? Since the electret itself is tied to gate and source, the
    limiting voltage is the max Vds of the FET. Sure, the load
    resistor drops some of the supply voltage, but by how much is not
    precisely predictable. The FET charcteristics are unknown; and
    even if typical values are given, there are tolerances - often as
    much as +/-50% for Idss. Then there's the swing from steady-state
    when there's an input. That swing may be of the order of
    millivolts under normal signal conditions, but there could be
    circumstances, intended or unintended, where the swing is much
    more, theoretically up to the P.S. voltage.
    In typical applications, yes. But what if I or someone else want
    to use the unit in an Atypical application? For example, I may
    want to keep circuit component count to a minimum by supplying
    the mic directly from a convenient, well filtered supply of +20V,
    but, for some reason, also want to keep the load resistor low. Or
    even use an inductive load. The max Vds (and possibly
    dissipation) rating will then be the ultimate limiting factor.
    See above.
    That was uncalled for. But I'll take it in the spirit of Usenet
    and just shrug.
     
  7. Phil Allison

    Phil Allison Guest

    "pimpom"

    ** Because there is a resistor between the damn PS and the FET !!!!

    The numbers are not the same nor simply related.


    (snip more mind numbing drivel)


    ** Err - like ones that actually work ??


    ** The YOU spell it out for us - fuckwit.



    ** Pure lunacy.


    ** Piss off - you ridiculous WANKER !!



    ....... Phil
     
  8. pimpom

    pimpom Guest

    I can't believe that you don't know the difference between limits
    imposed by voltage and that by current.
    Can't you imagine using a device for anything other than its main
    application? I can. Like using a screwdriver as a lever when
    nothing else is available. It "actually works", you know. I just
    take care to select the proper size.
    When someone asks you for directions to a place, do you demand
    that he reveals everything he intends to do in that place? Maybe
    *you* do at that. I simply asked if anyone knew the max voltage
    rating. What I want to do with that information is my business. I
    did NOT ask for help in designing something or if an electret mic
    is suitable for a specific application. I simply asked for one
    piece of information. If you don't know, shut the **** up. Moron.
    It's people like you who are driving others away from Usenet. And
    yet you blame GG, newbies and anything else you can think of
    except yourselves. Move your ass up out of your chair and go see
    a shrink. You need some serious therapy.
     
  9. Phil Allison

    Phil Allison Guest

    "pimpom"



    ** Piss off - you ridiculous FUCKING WANKER !!
     
  10. pimpom

    pimpom Guest

    You're repeating yourself. Yawwwn.
    Can't think of any argument that makes sense, eh?
     
  11. Phil Allison

    Phil Allison Guest

    "pimpom"

    ** Get fucked you vile little shit.
     
  12. pimpom

    pimpom Guest

    Oh, I do. All the time. OTOH, how long has it been since you got
    laid - not couning those desperate homo sessions? A year?

    You can congratulate yourself on one thing, though. Although
    you're only the third person I've ever flamed over the internet,
    you're the very first on whom I've ever used vulgar language. You
    must have caught me in a good mood. Congratulations.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-