| 摘要 |
748,460. Sawtooth generating circuits. ELECTRIC & MUSICAL INDUSTRIES, Ltd. July 8, 1954 [July 17, 1953], No. 19827/53. Class 40 (6). In a sawtooth current generator of the " resonant return " type the H.T. supply for the driver valve is fed to an intermediate point on the primary winding of the output transformer and the damping valve is connected across a greater number of the primary turns than the driver valve. The driver valve 1 is fed with a sawtooth input wave and supplies the deflection coils 4 through a transformer 2, 3, the H.T. being supplied through the lower part only of the primary winding. The damping valve 5 is coupled across the whole of or at least a larger part of the winding. Negative feedback is applied to the damping valve through capacitor 14 and amplifier valve 13 and the time constant of capacitor 14 and resistor 17 may be such as to impose a falling sawtooth wave on the feedback voltage. Negative feedback is also provided by virtue of the fact that the lower part of the primary of the output transformer is in the grid cathode circuit of the damping valve. The amplitude of the output wave is adjusted by a potentiometer 20 which simultaneously adjusts the bias of both driver and damping valves. Potentiometer 18 is adjusted to ensure that the damping valve is always conducting. The input wave may alternatively be of pulse form, in which case the grid of the driver valve is coupled to the first anode of valve 13. In an alternative embodiment (Fig. 2, not shown) the feedback capacitor 14 is connected directly to the grid of the damper valve and cathode bias is provided for the damper valve so that adjust. ing the bias of the driver valve to adjust the output wave amplitude also adjusts the damper valve bias. |
