GB228935A - Improvements in electron discharge tubes for generating or amplifying electric currents - Google Patents

Abstract

228,935. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. Feb. 9, 1924, [Convention date]. Thermionic generators and amplifiers.-Relates to electron discharge tubes in which a perforated " toregrid, " carrying approximately the same voltage as the anode, is utilized in combination with the ordinary control grid to secure a negative-resistance characteristic, there being no back coupling between the anode and grid circuits. The device may be used as an amplifier or as a generator of high-frequency oscillations. An adjustable non-inductive resistance 10, preferably equal to the absolute value of the negative resistance of the system, is arranged to be common to the two current circuits formed between the cathode 2 and the foregrid 3, and the cathode 2 and control grid 4 respectively. The telephones 12 are inserted in the circuit of the anode 5. Fig. 2 shows the variation of the foregrid current ig<1>, and the anode current ia, as a function of the control grid voltage vg for a constant voltage on the anode 5 and foregrid 3, showing a negative resistance characteristic between the points C and D. This may be utilized say between the points P, Q. Fig. 1. When used for two-frequency amplification, the input is offered across a transformer 9, 8. An initial decrease in the voltage of the control grid 4 diverts electrons from the anode 5 to the foregrid 3. The growth of current in that grid circuit continues owing to the voltage fall across the resistance 10 until it absorbs practically the whole of the electron emission from the cathode. The corresponding fall in anode current is indicated in the phones 12.