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P channel mosfet

Discussion in 'General Electronics Discussion' started by klopar, Mar 13, 2017.

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  1. klopar

    klopar

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    Mar 13, 2017
  2. davenn

    davenn Moderator

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    what is U3 and U4 ?

    I assume the word you use "burden", you really mean "load"

    what are the loads and what are they powered by ?

    it sounds like you are exceeding the ratings of the mosfet


    cheers
    Dave
     
  3. Audioguru

    Audioguru

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    Sep 24, 2016
    Your schematic is a backwards negative image that I can barely see. Why not use black lines on a white background like everyone else??

    A Mosfet gets hot when its current is high and its gate voltage is not enough.
    The datasheet for your Mosfet says that with a gate-source voltage of 4.5V then its on resistance max is 48milli-ohms when it is cool. Then with 6A in it, its heating is 6A squared x 48mΩ= 1.73W which is almost its maximum allowed heating without having a heatsink.
     
    CDRIVE likes this.
  4. klopar

    klopar

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    Mar 13, 2017
    Hi,

    Thanks for your answer. U4 and U3 are connector (input and output positive voltage). Yes, I thought load. I use mosfet for switching on/off. Load (light) uses 10A.

    Best regards
     
  5. davenn

    davenn Moderator

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    that doesn't really make much sense

    where do the 2 pins of U3 go to when they leave this circuit ?
    show us.... tell us

    where do the 2 pins of U4 go to when they leave this circuit ?
    show us.... tell us
     
  6. klopar

    klopar

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    Mar 13, 2017
    Negative voltage is connected direct on the load. Pin 1 on U3 is output here I have connect positive load. On pin 2 I have connect Vcc 12V to 23V. I have 2 difrent channel to switch. U4 is the same.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The voltage you apply to the gate of the MOSFET is relative to the source terminal.

    There is no connection shown on your circuit been your gate voltage part of the circuit and the source terminal of either mosfet.

    I guess it's possible that your 12V Vcc and the sources son1 and son2 could share a positive rail, but that would be stretching credibility.
     
    davenn likes this.
  8. klopar

    klopar

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    Mar 13, 2017
    Last edited by a moderator: Mar 14, 2017
  9. Audioguru

    Audioguru

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    The Mosfet and all the other parts can be replaced with a piece of wire because the light is always turned on.
     
    (*steve*) likes this.
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    R2 should go between the gate and source.

    Pulling the input (connected to R1) to ground will turn the light on.

    It would be preferable to increase R2 to 10k (make it significantly larger than R1)
     
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