Patent GB-598970-A (GB)
Title: Improvements in electron discharge valve circuits
IPC: G05F1/52
Filed: 1945-05-11
Abstract: 598,970. Valve amplifying circuits. GENERAL ELECTRIC CO., Ltd., and MACKENZIE, R. B. May 11, 1945, No. 11857. [Class 40 (v)] [Also in Group XXXV] An electron discharge valve circuit for transmitting D.C. or slow-voltage variations between points at different D.C. potentials, comprises two electron discharge valves with a common resistance traversed by the cathode currents of both valves connected so that current variations in opposition are produced by the valves in response to a voltage applied to the common resistance. The arrangement may also be used to provide a voltage stabilising circuit which comprises a negative and positive resistance in series and connected across the output terminals, from which a voltage may be applied to the control grid of a valve connected in series between the input and output terminals. In Fig. 1, resistance 3 carries the cathode currents of valves 4 and 5, the points A and D having a large potential difference. Valve 5 acts as a cathode follower, the voltage across resistance 7 tending to equal that across valve 4, the voltage variations across resistance 7 then being approximately equal and opposite to those across resistance 8. The potential of the grid of valve 4 is fixed relative to H.T. potential. If resistance 7 equals resistance 8, a variation of current in valve 4 produces an equal and opposite variation of current in valve 5, so that the total current through, and voltage across resistance 3 is constant. The input variation is applied to resistance 2 through valve 1 which acts as a cathode follower. Thus the input voltage applied to resistance 3 appears without attentuation at the cathode of valve 4, affecting the individual but not the total currents in valves 4 and 5. An amplified version of the input voltage appears at the anode of valve 4, which may be fed to one deflecting plate of a cathode-ray tube. Amplification or attenuation of the voltage appearing at the cathode of valve 4 may be arranged by making resistance 7 respectively less, or greater than resistance 8, as the opposing current variation developed in valve 5 does not then equal the variation in valve 4, which causes the potential difference across resistance 3 to change. Fig. 2 shows the invention adapted to provide a voltage stabilising circuit. Valves 12 and 13 connected and operating as in Fig. 1, are connected between the input terminals E, F, and output terminals G, H, of a circuit. The output from the anode of valve 12, is connected to the grid of valve 11 which is in series between the input and output terminals, E. and G, so that voltage variations developed at the anode of valve 12 control the potential drop across valve 11. To consider the method of operation, assume the potential of G is constant, then variations in the potential of H appear in attenuated or amplified form (according to the relative value of resistance 14) at the cathode and also at the anode of valve 12. A rise in the potential of H therefore causes the potential drop across valve 11 to decrease, thereby raising to potential of G relative to E. Thus a variable input voltage at E and F may be stabilised to produce a constant output voltage at G and H. Modifications provide for valve 5 to have an anode load so that push-pull output for deflection may be obtained, and for resistances 3, 15, 7 and 8 to include some inductance or parallel capacity elements. The valves 4 and 5 may be in one envelope, and a separate amplifier may be provided for the control voltage from the cathode of valve 12.