Recently noticed on Mouser that the BF256B is being discontinued. Discontinuance Notice.
I do not want this thread to become a debate about FETs vs. BJTs. This has been debated countless times, and in my eyes both have their applications, and both can sound fantastic.
While the BF256B is still available (about 10k in stock), but the discontinuance makes me nervous about designing anything around it in terms of serviceability.
Are there any decent JFETs left for audio applications? The J111 and J112 are meant for use as a switch, so I can't imagine that they have very good linearity or noise performance. I'm not expecting anything that will perform on the level of the 2SK170, but is there anything that can at least come reasonably close for a somewhat reasonable price (such that buying enough to get matched pairs wouldn't cost a fortune).
I do not want this thread to become a debate about FETs vs. BJTs. This has been debated countless times, and in my eyes both have their applications, and both can sound fantastic.
While the BF256B is still available (about 10k in stock), but the discontinuance makes me nervous about designing anything around it in terms of serviceability.
Are there any decent JFETs left for audio applications? The J111 and J112 are meant for use as a switch, so I can't imagine that they have very good linearity or noise performance. I'm not expecting anything that will perform on the level of the 2SK170, but is there anything that can at least come reasonably close for a somewhat reasonable price (such that buying enough to get matched pairs wouldn't cost a fortune).
Last edited:
No EOL announcement on Onsemi website, or Digikey.
But no surprise that analogue discretes are disappearing fast.
Patrick
But no surprise that analogue discretes are disappearing fast.
Patrick
The J111-113 work just fine, depending on what you use them for. The vendors' categorizations are never exclusive: if they say it's a switch, it doesn't mean it's no good as an amplifier.
A concrete example: the BF256 you mentioned is made from the Fairchild process 50, according to the datasheet. Now if you look at Fairchild's AN-6696, page 4, the P50 process is advertized in ALL categories!
Finally, you have the 3rd sources like InterFet and Linear Systems advertizing 2SK170 "look-alike". However, I don't have any first hand experience with them; the dies sure look very different from the original Toshiba's. Any expert opinion out there?
A concrete example: the BF256 you mentioned is made from the Fairchild process 50, according to the datasheet. Now if you look at Fairchild's AN-6696, page 4, the P50 process is advertized in ALL categories!
Finally, you have the 3rd sources like InterFet and Linear Systems advertizing 2SK170 "look-alike". However, I don't have any first hand experience with them; the dies sure look very different from the original Toshiba's. Any expert opinion out there?
The Toshiba 2SK2145 is a dual JFET in a 5-pin surface mount package. The source of the two JFETs are tied together.
Thanks to Zenmod for pointing out this device.
My thought is that the GR grade part can be turned into a 3-pin part with the two JFETs in parallel yielding an equivalent to the 2SK170BL.
To that end, I have ordered a handful along with an SMT adapter card to use in my plug-in proto board curve tracer fixture. I will compare to the Punkydawgs genuine 2SK170.
Thanks to Zenmod for pointing out this device.
My thought is that the GR grade part can be turned into a 3-pin part with the two JFETs in parallel yielding an equivalent to the 2SK170BL.
To that end, I have ordered a handful along with an SMT adapter card to use in my plug-in proto board curve tracer fixture. I will compare to the Punkydawgs genuine 2SK170.
Most TO-92 FETS have disappeared recently, along with several TO-92 BJT's. Several now have SMD replacements like the BF545 looks to be the BF245. Just means having to use SMD techniques.
Thank you for the link. Nice job analyzing the JFETs.
I will compare the individual JFETs inside the 2SK2145 and see how they match. If they do not match, then I may be better served using the 2SK209 for my purposes.
Just bought some 2sk208gr, from Arrow, anyone try them out ? low input capacitance, low noise, lower gain.
> I will compare the individual JFETs inside the 2SK2145 and see how they match. If they do not match, then I may be better served using the 2SK209 for my purposes.
They don't; there is no spec.
Expect you have 30% of say 100 pcs outside 3% between the two.
I measured 100's.
> Just bought some 2sk208gr, from Arrow, anyone try them out ?
Yes.
NECX and NESX Single-Ended to Balanced Converters
XCEN Balanced to Single-Ended Converter Revisited
😉
Patrick
They don't; there is no spec.
Expect you have 30% of say 100 pcs outside 3% between the two.
I measured 100's.
> Just bought some 2sk208gr, from Arrow, anyone try them out ?
Yes.
NECX and NESX Single-Ended to Balanced Converters
XCEN Balanced to Single-Ended Converter Revisited
😉
Patrick
Thanks, I wasn't aware of the 2SK208. Sounds like the market for through-hole JFETs is very, very small. I can certainly live with SMD, just makes it a little harder to breadboard a design, which is a small price to pay in the grand scheme of things.
Does anyone know if the 2SK208 would be quiet enough for me to get away with using it for the front-end of a microphone preamp? I know BJTs are traditionally the choice for this application, but I was thinking it could be interesting to try a FET front end if it can be made quiet enough.
Does anyone know if the 2SK208 would be quiet enough for me to get away with using it for the front-end of a microphone preamp? I know BJTs are traditionally the choice for this application, but I was thinking it could be interesting to try a FET front end if it can be made quiet enough.
To be honest it's pretty easy to get a SOT-23 mounted onto a bit of Veroboard, and then you can solder 3 solid core wires from there to go into your breadboard. Or if you've got really steady hands just solder the 3 bits of wire to the SOT-23 pins 🙂
Shame about that, it was the most viable replacement for the venerable 2N3819.
BC556B and MPSA42 bjt's also on that list. Popular for low noise and power amps respectively.
BC556B and MPSA42 bjt's also on that list. Popular for low noise and power amps respectively.
I think only the OnSemi devices are being discontinued, but the Fairchild ones are not - if that makes sense. Looking them up on Mouser seems to suggest this is the case.
Sorry to rain on your parade, but On Semi owns Fairchild. And when Daddy says stop, it's only a matter of time... 🙁
I think so, compare it to your other options.
I just received mine, Arrow delivers them free, next day.