Amplification factors and mutual conductance of a beam power valve

Analysis has been carried out for the determination of the distribution of electric field in a beam power valve when the control-grid pitch is larger than the cathode-control-grid distance. The method followed is an extension of the one suggested by Fremlin for a triode valve. Expressions have been derived for the various amplification factors, ¿, and it is shown that, in general, these factors vary along the surface of the cathode. It is further shown that the earlier expressions that have been derived give only the average values of the amplification factors. Expression for mutual conductance, gm, has also been considered for the beam tube. It is shown that, by taking account of the so-called inselbildung effect, arising out of variation of ¿ referred to above, close agreement between theoretically computed and experimentally obtained characteristics may be secured.