With my last couple of orders of matched jfets from punkydawgs, he sent me metal covers. How would I use them? They’re too big to fit over the pairs unless I filled them with something. The jfets are for an aleph j (already built) and an f6 I’m just starting.
Thermal coupling. His ad shows them potted in the can.
"Mount transistors face-to-face using heat shrink tubing and
a slight wisp of thermal grease, then fill the can with 2-part epoxy."
https://www.ebay.com/itm/254547580847
"Mount transistors face-to-face using heat shrink tubing and
a slight wisp of thermal grease, then fill the can with 2-part epoxy."
https://www.ebay.com/itm/254547580847
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I just glue my matched parts together face-to face with a filled epoxy. JB Weld gets the job done, though it takes a while to harden. JB Kwik is a lot faster. Arctic Silver might have better thermal conductivity, but it is considerably more expensive, and what you are aiming for is for the thermal resistance between the matched parts to be much less than that of the thermal resistance to the ambient environment. I haven't seen any serious offset drift in parts that I've bonded together this way.
They’re included for free. I used heat shrink on my alepha j but I might try them. It would suck if one of the jfets needed to be replaced though.
I keep well-stocked with JFETs and small-signal MOSFETs for making matched pairs, but then, I'm kinda a fanatic that way...
Papa Nelson sez, if you find a part you like, buy a bunch of them, as you don't know how long they'll be around.
Papa Nelson sez, if you find a part you like, buy a bunch of them, as you don't know how long they'll be around.
If the jFETs are of metal can type (TO-5) then you can use a piece of aluminium block with holes that snug fit (0.32 in). With TO-92 plastic package mount them face to face and fix with heat shrink tube.
But why you don't use a dual jFET to begin with?
But why you don't use a dual jFET to begin with?