Jfet Matching - Vgs of the J201

[chromesphere]

Hey guys,

I (finally) got around to testing some jfets and putting a couple in my p45 that were close in test result and it sounds much better, no question about it.  The phasing is a lot deeper.  But I had a question about some of the results I've found testing them.  I used Jacobs Jfet tester which I'm pretty sure is a version of R G Keens Jfet tester.  These numbers seem low.  Spec sheets saying "0.3v to 1.5v".  Would it be perhaps due to the high test conditions stated in the datasheet? (Vds = 20v opposed to my 9v?).  Or maybe that's just the way they are (out of spec)?  These are mmbfj201's which should be the same specs as its through hole fossilised brother.

Here's the results, any advice appreciated:

0.122v
0.065v
0.205v
0.056v
0.217v
0.114v
0.205v
0.131v
0.155v
0.129v
0.046v
0.072v

Cheers
Paul

[marauder]

Some info here.  I wonder if the fetzer valve matcher gets different results?

http://www.diystompboxes.com/smfforum/index.php?topic=97502.0

[chromesphere]

Thanks for the link marauder, ill have a read through, a little above my head but ill see if I can pound it in
Paul

[jkokura]

Your readings should be in '-', or negative Vgs. Perhaps you reading the wrong thing?

Jacob

[chromesphere]

Your readings should be in '-', or negative Vgs. Perhaps you reading the wrong thing?

Jacob

Nah, would have just had the leads around the wrong way

[marauder]

http://stompville.co.uk/?p=112

[chromesphere]

I wonder if the j201 needs more Rds?  I think I might just have to build up a p90 and see if these values are correct and will function properly.