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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Draw them yourself posted by Mark Kelly on September 27, 2005 at 16:58:39:
More for my own amusement than anything else I had a go at a version which accounts for current sharing between the screen and the plate and for the fractional effect of screen current on the output.This requires the addition of a factor (Rg2p) for the ratio of screen current to plate current at equal voltage (0.1 for 6V6) and an equation for the way this changes with voltage ratio. According to Spangenberg, "Vacuum Tubes" 1948 the current ratio varies as the fifth root of the voltage ratio.
Altogether, using Ik as derived from the modified Child Langmuir equation as before, we can now write:
Ip = Ik / ( 1 + (1-ULF) * Rg2p * fifthroot(Eg2/Ep))
This seems to give a reasonable curve with the slight "knee" near the Y axis typical of UL curves. I also shifted the Ep0 down to 200 Volts.
More is learnt from one bold error than from a hundred craven equivocations - Daniel Dennett
Mark Kelly
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Follow Ups
- More accurate version - Mark Kelly 05:27:56 09/28/05 (0)
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