14-09-2014, 04:38 PM
(This post was last modified: 15-09-2014, 09:40 AM by AlanBeckett.)
I fear I still don't understand it. While not disputing the 40mA figure I just don't know where it comes from.
As I see it there are two sources:-
First there's the Electron stream. But for Electron Current - Cathode to Anode - that implies that the Grid is the source of the Electrons. More sensible and plausible is an Electron flow from Cathode to Grid, ie a Conventional Current in the usual direction.
Second there's the Inter-electrode Capacitance. However, the 6F6 Data Sheet quotes 0.26pF for Cgk. That will be Pentode connected. So what about a Triode? ECC81 Data quotes 1.6pF. For a 'Modernish' Pentode, like EF91 it's quoted as <0.008pF. None of those figures seem to me to be capable of passing 40mA unless the Voltage and/or the Frequency is very high.
Alan
As I see it there are two sources:-
First there's the Electron stream. But for Electron Current - Cathode to Anode - that implies that the Grid is the source of the Electrons. More sensible and plausible is an Electron flow from Cathode to Grid, ie a Conventional Current in the usual direction.
Second there's the Inter-electrode Capacitance. However, the 6F6 Data Sheet quotes 0.26pF for Cgk. That will be Pentode connected. So what about a Triode? ECC81 Data quotes 1.6pF. For a 'Modernish' Pentode, like EF91 it's quoted as <0.008pF. None of those figures seem to me to be capable of passing 40mA unless the Voltage and/or the Frequency is very high.
Alan
