GB625741A - Improvements relating to sawtooth waveform generators - Google Patents

Abstract

625,741. Sawtooth generating circuits. FAUDELL, C. L. Aug. 13, 1946, No. 23914. [Class 40 (vi)] In a blocking oscillator for generating a sawtooth waveform in which a capacitor connected to the anode of a valve is charged whilst the valve is non-conducting and then rapidly discharged through the valve by the regenerative coupling between two other electrodes when it subsequently conducts, the sawtooth wave generated is made more linear by biassing a further electrode so that leakage from the capacitor through the valve before the rapid discharge commences is prevented. Fig. 1 shows a blocking oscillator in which capacitor 3 is charged from an H.T. supply through resistor 2 whilst valve 1 is cut-off and subsequently rapidly discharged when valve is rendered conducting by a positive synchronizing signal at lead 8. The suppressor grid is biassed negatively by the cathode network 11, 12 so that the valve is effectively cut-off during the whole of the time between its first being rendered non-conducting and the arrival of the subsequent initiating signal at 8. In a modification, Fig. 2 (not shown), the suppressor grid is biassed by connecting it via a resistor to the control grid circuit with a capacitor connecting it to earth. In the modification shown in Fig. 3 the suppressor grid is connected via a R.C. network 15, 16 across the secondary of the blocking oscillator transformer, the time constant of this network being long compared with that of the grid network 9, 10 so that the suppressor is still at a negative potential when the initiating signal appears at lead 8.