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

Thread Starter

s_mack

Joined Dec 17, 2011
198
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 :(
 
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strantor

Joined Oct 3, 2010
6,782
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.
 

GS3

Joined Sep 21, 2007
408
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JWHassler

Joined Sep 25, 2013
306
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.
I've done it... works fine, looks crappy
 

Thread Starter

s_mack

Joined Dec 17, 2011
198
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.
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.
 

Thread Starter

s_mack

Joined Dec 17, 2011
198
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.
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.
 

dl324

Joined Mar 30, 2015
16,845
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...
 

ian field

Joined Oct 27, 2012
6,536
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.
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.
 

GS3

Joined Sep 21, 2007
408
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?")
 

Thread Starter

s_mack

Joined Dec 17, 2011
198
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...
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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