A few months ago I ordered a few JFets from an internet site that had limited supply. I only ordered (4) LSK489 and (4) LSJ689. Results for Idss of the LSJ689 had a wider range than I expected (and the high Idss get noticably warm). There is no way to order grades like other parts such as LSK170, LSJ74, LSK389.
So if you need 2 pairs, I guess the safest thing to do is order 4 😕. I'm not sure changing ccs or source degeneration resistors is a better way to make up for good matching..
There's another supplier of Linear Systems that has many more parts in stock. Maybe better luck with them? Could others post results if you have them available?
LSK489: 3.41mA (A), 5.46mA (B), 6.04mA (B), 7.80mA (B)
LSJ689: 6.47mA (A), 7.10mA (B), 11.76mA (B-C), 14.56mA(C)
Attached picture of test setup, Vgs=0V, Vds=10V, measured using ammeter V+ to Vd for Ntype and Vd to V- for Ptype.
Also attached spice sim for all grades as reference.
So if you need 2 pairs, I guess the safest thing to do is order 4 😕. I'm not sure changing ccs or source degeneration resistors is a better way to make up for good matching..
There's another supplier of Linear Systems that has many more parts in stock. Maybe better luck with them? Could others post results if you have them available?
LSK489: 3.41mA (A), 5.46mA (B), 6.04mA (B), 7.80mA (B)
LSJ689: 6.47mA (A), 7.10mA (B), 11.76mA (B-C), 14.56mA(C)
Attached picture of test setup, Vgs=0V, Vds=10V, measured using ammeter V+ to Vd for Ntype and Vd to V- for Ptype.
Also attached spice sim for all grades as reference.
Attachments
Yes, they have LSK389 tightly selected in A, B, C and D grade, but then LSJ109 isn't matched (if you can find it at all), so end of the day the same story actually.
Earlier days LSK389 were without letters as well.
Earlier days LSK389 were without letters as well.