Triode Emulation (100% Sand)

[Nelson Pass]

The cascode linearizing trick for JFETs is neat, and I'll probably
even make use of it some day (into a high impedance, or with
a heavy duty follower). But definitely not a general purpose
emulation of any Triode working into any other load.

You're missing something. With a modulated cascode you can set the
loadline pretty arbitrarily. In ZV9 it's set against output current, which
linearizes against loads of varying phase and impedance. You can
also make it output voltage dependent, or a combination of both.

It's the JFET which has the triode-like character. You can perform the
same cascode tricks with triodes themselves.

 

[kenpeter]

Nelson, where exactly are you connecting this load
that you expect to see a Triode's plate? At the top
of the Cascode stack? (Two or three JFETs?, and
which JFETs are expected to be starved?), or is this
load connected somewhere else in the middle?
What impedance is your plate load expecting to be?

How does the load at the "plate" feed back to the
grid? To fake the Mu linearization and lower plate
impedance? A Cascode seems likely to isolate any
load at the top from participating in drain feedback
to the lower starved JFET, and would have a very
high impedance...

Perhaps I just don't understand the circuit you are
describing. I've read the patent, it may be far more
linear (in current) than an uncompensated JFET, but
it doesn't seem at all useful as a Triode emulator...
Unless you are also going to put Schade's voltage
feedback loop around the whole ball of wax?

I am not looking to fake a simple transfer curve into
a stable resistive impedance. I am looking for a full
set of Triode curves that can drive wildly variable
loudspeaker and OPT load lines with reasonably
faithful results...

Are you sure we are talking about the same thing?