Dr. Mazzola, you may wish to attend the upcoming Burning Amp Festival 2013 in San Fran. A chance to connect with Mr. Pass and a host of contributing audio DIYers. May even consider presenting a paper on....
just take your time , and be sure to not un-bottle that gray smoke
leave it inside , for joy and fun
Well, I got a little data today between this and that. Pretty dangerous methodology doing it that way but it took me all morning to get close? That's government, top secret, I can't talk about it stuff. Anyway, I gotta walk up to the equipment, make sure all the FuncGen stuff and voltage stuff is right, etc. and do a few manual triggers on the FuncGen, use the cursor on the scope and get some measurements. Write 'em down. Tweak the amplitude and offset of the FuncGen, reset the sweep on the scope and trigger again etc. Had to refine the test set-up a little... Maybe a little more will still be necessary... The graph I produced needs a few more data points but, between 1Vds to 4Vds I got a promising looking curve. Mabe a little like an LU deviceWasn't actually a curve but I'm gettin there...
I don't wanna be in a frustrated mode/mood or tryin to do 2 things at once(work thinks multi tasking saves money HA HA!) I need focus.
Like I said, excluding weather related problems, I'm good with that anway, I'll get somin done on the weekend if not sooner.
Keep plugging away. You should be my beta tester for my next analysis article, which uses software every DIYer will have, but requires quality feedstock data. I've been thinking during long showers how to encourage DIYer's to create feedstock data without using a high dollar curve tracer or letting Zen's gray smoke out. I think you're on to something.
Que Sera, Sera
The LU has an "input Cap"(Ciss) of 1150pF. The R100 data sheet calls typical Ciss 670pF!
Although... The LU parameter is spec'ed at some 10V D-S, something like the voltage we might use it at, (although the F3 might be 2.5Vds) whereas the R100 is spec'ed at 100V D-S where us Solid State guy's would probably not
The best I can say is, yes it will be an issue. But, I can't say how much or how much cascode will aliviate the issue. It likely depends on how we attempt any cascode modulation
flg. This is a neat Super Symmetric circuit. Dr. Mazzola; there is more on the performance virtues of a MOSFET-based power amp [invention] in the 2002 article by Mr. Pass entitled "Like Peanut Butter and Chocolate" at www.firstwatt.com.OK buzz, if you don't want to deal with the C of these parts, check out this balanced pre I was workin on some time ago. I avoid the capacitance issue by operating at + and - 80V
It will drive both sides of an F4!
I recorded enough data points to see that I might have chosen a random sample that has a higher than the typical Vgs value from the data sheet. So, I find from the graph below that we do not see that triode-like curve, as I thought I was seeing yesterday. Hmmmm 
Sorry about some of the details. X = Vds (V), Y = Ids (A).
Sorry about some of the details. X = Vds (V), Y = Ids (A).
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