GB285799A - Improvements relating to thermionic valves or electron discharge tubes - Google Patents

Abstract

285,799. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. Feb. 21, 1927, [Convention date]. Vacuum tubes.-The inter-electrode capacity of discharge tubes or valves with at least three electrodes is neutralized by a condenser of capacity substantially equal to that existing between the grid and anode, the condenser being separate from the electrodes and mounted within the valve with one plate electrically connected to the grid. The condenser 4, Fig. 2, may comprise internal and external metal coatings on a glass tube and may be mounted within the cap 2 of the valve carrying the usual pins 3, a lead 5 from a terminal 6 at the side of the cap being soldered to the inner coating of tin-foil and the outer coating being in contact with the grid lead. The condenser may be mounted in the foot of the valve. In a modification, the condenser comprises a metal tube spaced from the grid lead which forms one plate of the condenser. In a valve between leads 17, Fig. 5, to a tuned aerial and output leads 18 to another valve, the terminal 6 is connected to a coil 14 coupled to an anode coil 15 tuned by a condenser 16. If the capacity of the condenser 4 is equal to the capacity between the grid 11 and anode 12, the ratio of the coupling between the coils 14, 15 is one to one to neutralize self-oscillation and other effects due to the grid-anode capacity; if the capacities are not exactly equal, the coupling between the coils 14, 15 is adjusted. Specification 288,663 is referred to.