GB497865A - Improvements in or relating to electron tube oscillator circuits - Google Patents

Abstract

497,865. Valve generating circuits. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 1, 1937, No. 23928. Convention date, Sept. 10, 1936. [Class 40 (v)] In a method of generating oscillations of constant frequency, from the generated oscillations secondary oscillations are produced which are rectified and then converted into unidirectional pulses which are fed back to sustain oscillation. Oscillation is started in circuit 15, Fig. 1, by passing a momentary current through valve 14 whose grid is normally biassed below cut-off. The oscillating potential, Fig. 2, is passed through phase-shifting means 21, 19, an amplifier 20 and filter 22 so as to produce across resistance 4 a pure sine wave, Fig. 3, 90‹ out of phase with Fig. 2. A current then flows through anode 2 of the double diode triode 1 and the resultant voltage drop across 7 causes the bias of the grid 5 to drop below cut-off. As the wave across 4 passes through zero the charge on condenser 11 maintains a current flow through the resistance 7 so that the bias of the grid 5 cannot rise enough to allow valve 1 to pass a current. The second half of the wave passes current from anode 3 causing further current flow through the resistance 7 and the complete discharge of condenser 11. The bias of the grid 5 consequently drops again and finally rises to zero as the curve in Fig. 3 passes through zero. Thus the grid bias of valve 1 only rises to zero once per cycle, Fig. 4, and in doing so allows momentary pulses to fiow through its-plate circuit, at the same instant that the oscillations in 15 are at their maximum, Fig. 5. These pulses are passed to the grid of valve 14 so raising its bias above cut-off and allowing a pulse to pass to the tuned circuit 15 to maintain oscillation. Oscillation is started by closing switch 9 and output is taken at 25.