Discontinuation of 2SJ74 and 2SK170

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I realized this last year. The 2SJ74 is already gone. It was not in the main Toshiba catalog dated (I think) last August.
There are a considerable number of parts still in the distribution pipeline, so it's not necessary to panic. They'll be available for a while yet.

This is all old news, but for whatever reason it catches fire again from time to time.
There are no Toshiba low noise P-ch JFETs in production.
The 2SK170 is current through some time this spring--I forget the exact date. The 2SK389 has been gone for quite some time.
There is product in the retail pipeline, so you will be able to buy parts for a while yet.
As for why, I've not seen any formal reasons from Toshiba, but my working hypothesis is that they regard through-hole parts as obsolete and are eliminating all through-hole parts from their catalog. The answer to your next question is no...I do not know of any plans to produce surface mount low noise JFETs in the near future.
Try to be rational about this. I've seen people who won't use ten parts in their entire lifetime talking about buying a hundred, "Just in case!" Just in case of what? Martians land next door and demand that the DIYer build them a fratzenwhoosis so they can call home? Rather than panic and start hording parts you will never use, sit down and make a list of the things you might actually build and buy accordingly.

> Except for 400mW max power dissipation for 2SK170 compared to 200mW for 2SK370, I can not see other difference at first sight.
So why the 2SK170 is obsolete and not the 2SK370?

Because you can now make the same transistor on half the die size with advanced lithographic processes, and hence twice the number of transistors per wafer, and hence half the cost / die. The penalty -- half the dissipation because of reduced die area for heat transfer. But I guess the transistor still sells for the same price, and most people could do with 200mW. So it makes sense for Toshiba.

And as far as I know, 2SJ108 is active.

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