Are all FETS of SOT23 package going to have the same pin-out?

Discussion in 'General Electronics Chat' started by s_mack, Oct 19, 2015.

  1. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
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    I screwed up on a product design. Somehow I swapped the Gate and Drain on my schematic after getting the prototypes produced. I honestly don't have any idea how I did it, but now I have 500 fully assembled boards that don't work.

    I used an NXP 2N7002P. pin 1 is the gate. Is there any hope that I can find a SOT23 FET where pin 3 is the gate?

    Probably not, but thought maybe someone knew something. I've looked at half a dozen and they are all pinned the same :(
     
    Last edited: Oct 19, 2015
  2. GS3

    Senior Member

    Sep 21, 2007
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  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
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    Since G and S are swapped, could you just flip the FET upside down? I guess you'd need to bend the tabs the other way. Probably wouldn't look very professional. I've never done it, not sure how it would work out; just an idea.

    Well that proves not all are created equal. Too bad that one isn't created unequal in the way that would be beneficial. I wasn't able to find one with pin 3 as Gate.
     
  4. GS3

    Senior Member

    Sep 21, 2007
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    Shoot! I posted the wrong link. I believe the SMD version of that device has G to 3. Try
    http://www.nxp.com/products/rf/tran...ffect_transistors_for_switching/PMBFJ177.html

    Come to think about it you could probably substitute the through-hole version carefully placing the wires in place.
     
    Last edited: Oct 19, 2015
  5. JWHassler

    Member

    Sep 25, 2013
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    I've done it... works fine, looks crappy
     
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  6. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
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    I should have been clear that it needs to be n-ch. You had me excited there!

    I can do the through hole sub maybe, but to92 is physically too large for this application. Maybe i can find something smaller.
     
  7. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    I was confused why you thought that would work... then I realized my mistake when I posted. I meant DRAIN and gate, not source and gate.

    Pin 3 = gate is still what I am looking for.
     
  8. dl324

    Distinguished Member

    Mar 30, 2015
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    What is your clearance around the transistor? Have you considered having an adapter made? It would make the correction look more "professional"; particularly if anyone ever needed to replace that device.

    I know the part is very small and an adapter will be a pain to use. If it were me, I'd scrap the lot and start over. Taking short cuts like that could come back to haunt you...
     
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  9. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
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    Some RF types have pin layout options denoted by a suffix on the part number.

    But you'd be looking at Id not much more than 10mA and Vds around the 20V mark.

    There may be power RF types with pin options, but probably expensive.

    Look around the BFG part numbers.
     
  10. GS3

    Senior Member

    Sep 21, 2007
    408
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    You might try contacting the manufacturers directly. They might be able to help. ( I can imagine some guy there saying "shoot, I made a mistake and made these FETs with the wrong pinout, with the gate to pin 3, what can I do with them?")
     
  11. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    I hate getting advice that I should follow rather than what I want to hear :)

    You're probably right and I probably should scrap it. That is certainly an option. It sucks though... not just the expense of new boards, but also the lead time is much higher than doing a repair and I have customers waiting.

    I may have clearance for an adapter. I don't know if they can make a PCB that small though. Each adapter would need to be roughly 5mm square. I see on pcbcart.com (first one that came to mind) their minimum is 5x5 mm.

    Thanks for the idea!
     
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