The mu of a tube must be less than plate potential? Is it true?

It is a very interesting rule of thumb. [Atkins]


Perhaps it explains why the CV2269 electrometer tube can operate with only 1.2V at the anode, see Pleiades V1.


But perhaps with pull up bias (Pleiades bias) much lower plate potential operation is possible than amplification factor or μ.


Reference:


http://www.rfcafe.com/references/radio-news/low-plate-potential-tubes-january-1957-radio-television-news.htm