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Old 1st July 2014, 09:23 AM   #1121
bcmbob is offline bcmbob  United States
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OK, matched pair it will be. The footprint is shown here. Was just curious if some kind of creative twisting for face to face offered any advantage in operational stability. Most likely not worth the trouble in this application

Thanks.
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Old 1st July 2014, 11:18 AM   #1122
AndrewT is online now AndrewT  Scotland
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The middle pin of the 7 does nothing
The two sets of the outer 3 are the jFET pins.
One is reversed relative to the other.

holes 3 and 5 are the Source pins.

Turn the left jFET 90 anticlockwise after insulating the Gate lead.
Turn the right jFET 90 anticlockwise after insulating the Gate lead.

You now have a pair facing each other ready for Thermal Coupling.

One of the biggest advantages of the j109 is the Thermal Coupling.
The specified tolerances of matching are not worth buying.
Most pairs achieve much better matching than the tolerance.
But this can still be bettered by hand matching over a range of Id (<Idss).

With (very labour intensive) hand matching and Thermal Coupling you can end up with a better matched pair than using a j109.
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Old 1st July 2014, 01:11 PM   #1123
bcmbob is offline bcmbob  United States
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Thanks Andrew, I'll take a closer look at the data sheet and the traces on the board for a better understanding. Hopefully Buzz or Spencer will have something I can use.
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Old 1st July 2014, 01:13 PM   #1124
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There is a gentlemen in Swap Meet selling genuine J109's, if you are interested.
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Old 1st July 2014, 01:29 PM   #1125
bcmbob is offline bcmbob  United States
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Quote:
Originally Posted by buzzforb View Post
There is a gentlemen in Swap Meet selling genuine J109's, if you are interested.
Very Much so. Please supply info.

Edit: found it - PM sent. Thanks.
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Old 1st July 2014, 01:39 PM   #1126
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FS: Toshiba 2SJ109-V Dual JFETs
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