GB683302A - Improvements in or relating to apparatus including thermionic valves for generating electrical signals - Google Patents

Abstract

683,302. Valve circuits. GENERAL ELECTRIC CO., Ltd., ARBON, R. S., and HUNT, G. J. March 28, 1951 [March 28, 1950], No. 7795/50. Class 40 (vi). A valve generating circuit comprises a pentode type valve having a short third grid base and a feed-back connection between the anode and first grid so that over at least a part of the oscillatory cycle the valve operates with negative mutual conductance. Fig. 2 shows a saw-tooth generator in which the pentode valve 1 has a short third grid base and in which the third grid 7 is preferably closely wound so that if the second grid 3 has a potential above that of the cathode, but substantially less than that of the anode, and if the third grid 7 has a potential approximating to that of the cathode then if the first grid 4 increases in potential a critical point is reached at which the anode current decreases in value so that the valve has a negative mutual conductance. The pentode 1 is connected as a Miller valve, the feedback between anode and control grid being effected by capacitor C3 and the cathode follower stage 11. The anode potential of valve 1 runs down linearly in the normal Miller integrator manner as capacitor C3 discharges through resistor R3 until a point is reached when a further increase in the control grid voltage causes the anode current to decrease, the anode potential rises and the effect is cumulative so that capacitor C3 is rapidly re-charged from the H.T. supply and the cycle is repeated. The saw-tooth generator may be synchronized by an external signal. Fig. 3 shows a frequency divider and stepped waveform generator of the cup and bucket type in which the anode potential of the Miller valve 20 is reduced in steps by the positive input pulses fed in from capacitor C13 via diode 34 until the grid potential rises to the critical value at which the anode current starts to decrease when capacitor C12 is rapidly recharged and the cycle is repeated. Thus a stepped waveform is produced at terminal 32 having a repetition frequency which is a submultiple of that of the input pulse train. The input pulses are applied through a buffer stage comprising valve 35.