CIRCUIT analysis

Discussion in 'General Electronics Chat' started by amit080391, Jul 13, 2012.

  1. amit080391

    Thread Starter New Member

    Jul 13, 2012
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    Is led will glow or not??
    IS this circuit correct ??
    when we speak in microphone which is connected
    ANSWER FAST
     
    Last edited: Jul 13, 2012
  2. KCHARROIS

    Member

    Jun 29, 2012
    292
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    I dont see why the led wouldnt turn on. The microphone does produce a small current. But since you have 2 transistors the gain would should be high enough to give enough current for your LED.
     
  3. amit080391

    Thread Starter New Member

    Jul 13, 2012
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    Is this circuit ok or not??
    LED will glow or not
    ???
     
  4. BillB3857

    Senior Member

    Feb 28, 2009
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    Is this a homework assignment? If so, let us know what you think and why. We'll be happy to help you learn, but not happy to do your homework for you.
     
  5. amit080391

    Thread Starter New Member

    Jul 13, 2012
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    sir i think it will work because when input from mic goes to bjt gate terminal , bjt will operate and other bjt will also work and we will get output and led will glow ....!!!
     
  6. bretm

    Member

    Feb 6, 2012
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    Which is pretty much what kcharrios said.
     
  7. amit080391

    Thread Starter New Member

    Jul 13, 2012
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    sir i want to ask for confirmation that it will work or not??
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    I think the electret microphone is connected incorrectly and the values of R3 and R4 are wrong.
     
  9. bretm

    Member

    Feb 6, 2012
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    My understanding of electret microphones is that they are used for the voltage they provide directly, instead of being used to modulate at existing current flow like in the circuit shown. So that part is weird.

    But the LED would light even if the microphone were ripped out of the circuit. In that case, Q1 would be cut off, so Q2 would get 9mA of base current and would turn on hard.
     
    Last edited: Jul 13, 2012
  10. bretm

    Member

    Feb 6, 2012
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    Message removed
     
    Last edited: Jul 13, 2012
  11. KCHARROIS

    Member

    Jun 29, 2012
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    If you always want the LED to always be on do it this way like my schematic. I just moved the mic and coupled it to the transistor base.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    I think that the electret mic and 330 ohm resistor will turn on the first transistor all the time so it turns off the second transistor all the time. An extremely loud sound might make the LED blink.
     
  13. WBahn

    Moderator

    Mar 31, 2012
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    Whether the circuit is correct depends entirely on what the circuit is supposed to do, which is not stated anywhere. Don't make people guess.
     
  14. bretm

    Member

    Feb 6, 2012
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    At least we ANSWERED FAST. :)
     
  15. absf

    Senior Member

    Dec 29, 2010
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    I think the 220 ohm for biasing Q1 is too low. It would make Q1 saturate.

    But the mic should work well under this condition.

    Allen
     
    Last edited: Jul 13, 2012
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