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In Reply to: RE: One vote for "Triode", one for "Modulator" but I like "Special Triode Connection" posted by Steve O on November 13, 2021 at 17:30:38
I recall many years ago that David Berning published curves for his screen driven output tube configuration. The curves were VERY linear and triode-like. This does require a hefty voltage swing, but that is not an insurmountable problem by any means.
Follow Ups:
...g2 drive does appear to be more linear (curves are more evenly spaced) than conventional pentode g1 drive but based on published data and limited personal design experience, I find it difficult to believe that a true triode characteristic is achieved. A healthy dose of corrective feedback could change effective curves significantly.
Unfortunately I don't remember where they were published. It was probably 35-40 years ago. Yeah, I'm old.
...Berning's website looking for the curves for g2 drive. Didn't find any but I did find Berning's patent for g2 drive #3,995,226 dated Nov. 30, 1976. Primary benefits/characteristics cited are increased reliability at high anode voltage, cooler operation and "..linear, highly efficient operation resulting in relatively high power output.." . Nowhere is triode or triode-like operating characteristics mentioned. The circuit is as I described earlier where g1 is strapped to the cathode and drive applied to g2. Read it for yourself at the link above. Seems to be an interesting error in the second paragraph of "BACKGROUND OF THE INVENTION".
Diodes?
I assume the patent writer intended to use "tetrode" or "beam tetrode" where diode shows up. OTOH, Berning is innovative and maybe he envisioned an output config. somehow using diodes instead of traditional control grid devices. Who knows?...David Berning knows!
Thanks Gary. Both David and Murray Zeligman told me the curves were triode as did the designers of the Melos amps. The biggest problem was getting full power from the output tubes since screen drive needed high current to drive to full output. David used a bipolar transistor. Melos used MOSFET followers on the driver tube. I believe David later built a 100 full tube version with tube driver.
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