Amplitude Of Triode Oscillations

Extract

BY a simplifying assumption we express amplitude, reaction, frequency, and change of plate current in triode oscillations in terms of the fraction of the time during which plate current is flowing. The mathematical methods are simple, and were used by E. V. Appleton and B. van der Pol, Phil. Mag., 43, 177, 1922.

A triode is an exhausted glass vessel containing three electrodes: a filament or heater, a grid, and a plate. Electrons emitted by the heater are caught on the grid and plate in numbers depending on their potentials, and constitute currents from the leading-in wires towards those electrodes, called the grid current and plate current. If V_gis the potential of the grid relative to the heater, and V_pthat of the plate, the plate current I_pis theoretically and experimentally a function f(V_p + μV_g) of V_p + μV_gover a large range, where μ is a constant called the amplification. Thus the curves of I_pfor different plate potentials V_pare obtained from each other by translation parallel to the axis of V_gby an amount proportional to the change of V_p. The grid current is much smaller if the grid potential is not too high.