On 2021-11-29 1:21 a.m., HF via groups.io wrote:
Hi Toby,
Thanks for your suggestions!
I had read of references to the 2N5454 and 2N4416 elsewhere in this forum. Once I looked in the document Michael referenced, I found out where those came from. The table describing the matching technique says it's from the 2N4416 "family" and a later page refers to the part itself as a 2N5454. I was able to find specs on both of these devices, but I'm not sure that those are the specs that pertained to the era when Tek was building these instruments. For example, the TO-92 package isn't mentioned, and the 2N5454 is described as 2 devices in one can, not individual devices. But it's all I have, so I put these two at the top of my table for checking other JFETs for potential substitution.
I just looked up Linear Systems; I hadn't heard of them until I saw your post. It looks like that company is geared towards providing devices for which mass-produced devices are inadequate. I'm afraid I would be pestering them if I were to call them with a hobbyist need. But I might still do that, once I study the circuit some more and think I understand it well enough to know why the devices need to have the characteristics on my list.
Hi Halden
It is weird that Linear Systems is so obscure on the web.
I found them very helpful and accommodating with a small/hobbyist order, so I wouldn't hesitate.
It looks like I'm experiencing mission creep. At first I just wanted to get this 'scope working. But now I see an opportunity to learn something about JFETs and JFET circuits.
Same! There's a Teledyne book online that might help:
"The Art of Electronics" also covers them in some depth.
--Toby
Cheers,
Halden
