It's fine for now, but I still question if I should be designing equipment around a part that On-Semi wants to obsolete. Most likely it's only still in production because a government client told them to keep it in production... so we'll see how long that lasts.
Thanks Mark, this explains a lot I didn't realise. I noticed the increase, but not the cause.
P jfets...availability... now that's a challenge!
It serves more issues.
Is that a checked fact or an assumption?
I rather think it's market and shift from discretes.
Availability here is ok, but not as twenty years ago, admitted.
Purely a guess, but my conclusion was reached based on the fact that On-Semi redacted their decision to cease production of the BF256B a few months after the initial discontinuance notification. I have a hard time believing that there was that much of a market demand to make them do that.
Also, it's all well and good to us P-channel JFETs, but can anyone list any good low-noise ones that are still in production?
Could it be that the decision to keep the BF256B going was aided by ON Semi taking over Fairchild? Perhaps Fairchild had a cheaper line manufacturing them?
But yes I agree, there might be some military app that needed them...
But yes I agree, there might be some military app that needed them...
I believe that the On-Semi acquisition of Fairchild pre-dates the announcement of obsolescence by about three years.
Entering ~BF256B parameters into the On-semi selector gives BF256B and MMBF4416.
MMBF4416A is slightly cheaper and 35V instead of 30V.
MMBF4416A is slightly cheaper and 35V instead of 30V.
I question the actual availability of the MMBF4416A since all the major distributors have 0 stock. The 2SK3557 is a lower voltage part IRRC, but it is relatively available still.
Farnell in the UK now have some BF256B devices on order. ON Semi reactivated these in October last year.
Another approach if you want future-proofed matched JFET pairs is simply to leverage the best JFET input opamps like the ADA4625-1. 3.2nV/√Hz, 4.5fA/√Hz, < 80µV offset.
Yes you've only got single-ended output, but FET input opamps aren't going away anytime soon and the matching is not going to disappoint!
Yes you've only got single-ended output, but FET input opamps aren't going away anytime soon and the matching is not going to disappoint!