A one-half watt heater power reduced size Nuvistor triode:
http://www.dtic.mil/dtic/tr/fulltext/u2/294926.pdf
A amazing report including the biography of the great team behind the development of Nuvistor electron tubes at RCA. Of course a very skilled woman Margaret Deevy fabricated many of the critical parts.
Page 149 shows very low voltage curves.
From what is understood by the high grid to cathode current and use of cathode bias resistor, Pleiades or anode to grid bias was not known at the time. The Pleiadss or anode bias leaves the control grid independent of the cathode circuit. (Ooops no, it seem they knew, see end of this post).
Whereas if a resistor is returned from grid to cathode there is a considerable current flowing in the input circuit since the cathode is positive (by the emitted missing electrons). When a resistor is connected between cathode and grid the positive cathode pulls electrons externally through the grid so that it gets back electrons that have been emmited.
The d'Alembert principle may possibly be used to get more insight into these phenomena.
Later addition:
It seems they knew. On page 20 of this brilliant report we can see the title transconductance measurements. "...Some of the measure- ments of transconductance which are shown later in this report are made in a special manner in that the grid is operated at approximately space potential The circuit being used to measure transconductance is shown in Fig. 4. It will be noted that the grid is returned to a positive ten volt supply through a 20 megohm resistance. This will assure a constant value of one-half microampere of grid current. The plate of the tube under test is returned to a variable positive..."
Hmm
Reference:
The Pleiades bias - euroelectron
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