was going through the Fairchild website and found these Jfets as I see they have low pf and good Yfs and yet low noise. Can we use these instead of 2sk170 and 2sj74?
maybe pair of them , in each position
however , 50 greenies for LSK from Store is hardly greatest investment in entire amp , while critical position
however , 50 greenies for LSK from Store is hardly greatest investment in entire amp , while critical position
I see it in more datasheets from JFET's: "Sourced from process 51" .....
What does that mean? What is the manufacturer trying to tell us with that information?
What does that mean? What is the manufacturer trying to tell us with that information?
I bought a bunch of them a few months ago to play with and/or use as CCSs to save on SK170s.
The Idss was too much in all of them. Around 17-20mA.
The Idss was too much in all of them. Around 17-20mA.
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Papa explains it nicely on the F5T article (page 5)
Although I can't remember if vanilla runs on lower V.
At 8mA they operate close to 200mW
You can get away with a bit above that, but you have to ensure proper ventilation
20mA (will work a bit lower because of the degeneration) will push them close or above max power dissipation levels
So you will probably have to increase the degeneration resistors to tame them
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will be hardly using in 2.5ma so I believe there is no need of heatsinking on them.
xconductance , degeneration , Idss , thus value of drain resistors to open mosfets ..... at least OLG (and control of output gates) is going doooooown
no way Jose ...... plenty of factors to solve successfully , and to have much worse than original
as I sad 50 bucks for LSK is peanuts in overall sum , especially when you count what's price of original FW F5 ........ and we got all what's important ( both brain and ball$ ) for nuttin'
so , too much of cheapskatin' is on verge of disrespect ...... and deeply in foolishness
(said ZM, biggest cheapskate of all Greedy Boyz)
no way Jose ...... plenty of factors to solve successfully , and to have much worse than original
as I sad 50 bucks for LSK is peanuts in overall sum , especially when you count what's price of original FW F5 ........ and we got all what's important ( both brain and ball$ ) for nuttin'
so , too much of cheapskatin' is on verge of disrespect ...... and deeply in foolishness
(said ZM, biggest cheapskate of all Greedy Boyz)
I have approx. 500 of each - J309 and J271
even if these are on par with Toshibas (and LSK) with xconductance , I can use them instead of Toshibas only in stages where biasing is via CCS or something , without too much influence of degenerating resistance
in F5 ( and other stages where biasing is made through source impedance ) , Idss is of same importance as xconductance
F5 is soooooo optimized , that any change will result in practically completely different amplifier
doable , possible , even resulting in great amplifier ..... but task not for someone in need to ask simple questions
not mocking or disrespecting anyone , just stating the facts
even if these are on par with Toshibas (and LSK) with xconductance , I can use them instead of Toshibas only in stages where biasing is via CCS or something , without too much influence of degenerating resistance
in F5 ( and other stages where biasing is made through source impedance ) , Idss is of same importance as xconductance
F5 is soooooo optimized , that any change will result in practically completely different amplifier
doable , possible , even resulting in great amplifier ..... but task not for someone in need to ask simple questions
not mocking or disrespecting anyone , just stating the facts
[emoji23][emoji23], sometimes situation could be to gift an amp to one of your family member or a friend, because you loan Speakers from them....no way I am parting with my 2SK’s for a gift...want to live with guilt, but not JFET’s
There are 9,876 different JFET part numbers.
There are basically about 13 JFET masks (the Silicon layout).
Some parameter adjustment is possible "in the oven" with dopant concentration and cooking time, but not a lot.
Say you make a lot of cookies. Even using the same spoon, flour, lard, oven setting, they don't all come out identical. Soft, crunchy, plump, flat. Same in JFET processing. Vto and Idss will vary over a wide range. This influences Gm. Leakage and breakdown voltage also vary a lot.
So the JFET maker runs "process 50", and then *sorts* the resulting parts. Parts with "good" parameters are sold under "good" part numbers and should fetch "good" price (in an ideal world). Lesser parts may be plenty fine for some users, if they can pay less. That's how we got so many part-numbers from a limited range of basic Processes.
Processes 50 (51?) is perhaps the most popular. Just a good all-purpose size and parameters. My book is packed away. I recall another with very small size for low-low leakage, one of huge size for low Ron, and a dual (which seems to be obsolete).
But they were all of them deceived. For another one was made... In the land of Japan. In the fires of mount Fuji, Sauron forged a master process...
One jfet to rule them all 🙂
One jfet to rule them all 🙂