Flicker noise resistance in vacuum tubes

The flicker noise work at the University of Minnesota has shown that the best 01erating conditions for a triode are a grid bias of -1.5 volts and a plate voltage adjusted such that the plate current has a value between 3OO μa and a few ma. The flicker noise resistance as a function of current is then almost constant in that current range; its value usually increases with decreasing current for very l0w currents. The first result is compatible with the theory of space-charge suppression of flicker effect, the second result can be explained by a decrease in effective cathode area (island effect). The influence of this result upon the choice of cathode area will be indicated.