Positive-Grid Characteristics of Triodes

The total emission current in a vacuum tube can be expressed by the familiar space-charge equaion. This paper shows theoretically that the ratio of plate current to total current should be a function only of the ratio of grid to plate voltage, and introduces experimental data to show that the function can be represented by a single exponential term. The exponential function is combined with the space-charge equation to obtain an empirical equation for the positive-grid plate-current characteristic. A simple, experimental method of obtaining the constants in this equation is described.