GB515786A - Improvements in or relating to electrical oscillation generators - Google Patents

Abstract

515,786. Valve generating circuits. WHITE, E. L. C. April 13, 1938, No. 11281. [Class 40 (v)] To stabilize the frequency of a blocking oscillator or multi-vibrator, the load impedance is made so large that in operation the electrode associated with the back coupling swings to substantially cathode potential so that the charge on the condenser is substantially independent of the valve constants. Preferably the discharging resistance of the grid condenser is connected to a bias positive with respect to the cathode which is comparable in magnitude with and derived from the supply potential for operating the generator. A blocking oscillator circuit is indicated in Fig. 1 the leak resistance 12 of the grid condenser 10 being connected to the cathode 2 of valve 1 through resistance 14 and part of resistance 13, the two resistances being connected in series across the generator supply 9. The valve used should be capable of passing high anode current for a quite low anode potential and is preferably a pentode. The output as shewn.is taken from the screen 4 but it could be taken from the anode 6, if the back-coupling condenser winding 7 were connected to the screen 4. A multivibrator circuit in which one discharge resistance 21 is connected according to the invention is indicated in Fig. 3. This circuit generates very short pulses, the time constant of 25, 29 being made small. A circuit in which both valves are pentodes and both resistances 29, 21 are connected to tappings on potentiometers as 22, 23 across battery 24 is also described.