GB308085A - Improvements in or relating to thermionic generators and the like - Google Patents

Abstract

308,085. Dicker, S. G. S., (Naamlooze Vennootschap Philips' Gloeilampenfabrieken). March 19, 1928. Thermionic generators and amplifiers.-Thermionic oscillation generators, of the self-excited or separately-excited types, have one or more discharge tubes connected in the grid-leak circuit, the breakdown voltage of these tubes being at least equal to the required minimum negative grid voltage, and a voltage source at least equal in value to the breakdown voltage is connected in parallel with the tube or tubes. As shown in Fig. 2, the grid circuit of the valve 1 is coupled through the coil 6 to a master oscillator. The grid leak path comprises a choke coil 7, a resistance 8, and one or more sets of glowdischarge tubes 9, 15 with separate series resistances 18, 19. When the valve 1 is in operation, the grid becomes more and more negative until the tubes break down. Should the valve cease to operate, the grid is held negative by the transformer 14 and rectifier 13 which are connected. in series with a resistance 12 across the discharge tubes 9, 15. The transformer 14 may be fed from mains. The negative bias is smoothed by a condenser 26. A battery may replace the transformer 14 and rectifier 13. For the selfexciting oscillator shown in Fig. 3, the glowdischarge tubes may be replaced by a triode valve 21, the grid 23 of which is negatively biased by a battery 25 so as to pass current only when the grid voltage of the main valve 1 has reached a required value.