JFET Testing Sanity Check

Erik S

Well-known member
I'm getting my parts together to build a Viceroy, and reading through @Chuck D. Bones development thread for that circuit:


Chuck used PF5102 JFETs (Which I have, so far so good) and recommends something with a Vp no larger than 2V.
Following along in that thread, I pulled out a breadboard to build a test rig. (Figure 10 on this page):


After testing my whole stash of ten PF5102s and looking at the datasheet, I realize that larger that 2v would be out of spec for a PF5102, and maybe none of this was necessary, but here's my dumb question:

Per the datasheet:

Vp (Vgs off) for a PF5102 should be between -0.7 and -1.6

Idss should be between 4.0 and 20 mA


The values from my test rig appear to be in spec except that my Vp numbers are positive instead of negative.
Did I do something wrong, or is the polarity irrelevant?

F0E479A3-EFF0-408C-8434-0D932C1DE9DF.jpeg
969861FD-C26C-488F-B253-9E961DC7935C.jpeg
 
My non-technical solution: could just socket the slots and audition what you have in there, since you already have a supply to choose from.
 
My non-technical solution: could just socket the slots and audition what you have in there, since you already have a supply to choose from.
Yeah, I think I’m all set to move forward with the build using any of these, I was just trying to figure out if I did something wrong with the tester I built.
 
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