Thanks for the link. It makes for interesting reading. At the very
end, complete conversion kits are mentioned for specific instruments
like the Tektronix 500 series CA amplifier and the Hewlett-Packard
HP500 VTVM.
Teledyne used the cascode configuration with internal bias since they
were replacing triodes. They had their own high voltage JFETs which
simplifies the design although high voltage enhancement or depletion
mode MOSFETs could be used now. High voltage high frequency bipolars
would be useful if they were available. In my case, I can just lower
the anode supply voltage.
On Sun, 27 Jan 2013 16:47:33 -0000, "Ed Breya" <edbreya@...>
wrote:
I just stumbled onto this blast from the past while looking for other info, and immediately remembered this discussion. It looks like Teledyne had the direct substitution problem solved in the 1970s. Hope this helps with cascode ideas - I don't know if the high voltage JFETs are available anymore.
)_Misc_Test_Equipment/FETRON_Solid_State_Vacuum_Tube_Replacement.pdf
Ed
David Hess