Abstract
It is already well known that the frequency of oscillation of an audiofrequency triode oscillator is different from the natural frequency of the oscillation circuit, as calculated by the formula ω02=1/CL•.
The discrepancy which amounts to several % in certain cases depends upon the circuital constants as well as the valve conditions such as the filament temperature etc.
Explanation is here given from the point of view that the grid current the principal cause of the variation.
For the sake of simplicity the author considers the case in which the instantaneous value of the plate potential is throughout its pulsating cycle always higher than the grid potential, so that the grid current may be considered as a function of the grid voltage only.
The actual frequency ω is related to the simple theoretical frequency ω0 by the equation:
ω2=ω0 2[1-kx0 2MLg/(rp+Rp)(rg+Rg)]……(13)
The effect of the grid current upon the amplitude of the oscillation is φ considered for the case of small amplitude, and the following equation is given for the amplitude of the plate current pulsation:
a2=a0 2[1-1/aG(kM/L-1)(M/CR)4]……(23)
where a0 denotes the value when the grid current is negligible.
In the next place, the oscillation characteristics are observed dynamically by means of the Braun tube oscillograph. It is ascertained that the hysteresis loops, which become apparent when either the frequency or the intesity of the oscillation is increased, are due to coming into existence of the grid current.
This paper includes the following topics.
I. Introduction.
II. Effect of grid current upon the frequency.
III. Experiments as regards the frequency variation.
IV. Dynamic oscillation characteristics.
V. Effect of the grid current upon the amplitude.
VI. Conclusions.
