Partition components of flicker noise

The flicker noise fluctuations in the space current of a thermionic valve are reduced by operating the valve under space charge limited conditions. In a pentode, this ¿smoothing¿ is less effective due to the division of the current between the anode and the screen grid; consequently, a partition component of flicker noise may be said to occur. Experiments are described which confirm the presence of this phenomenon and which give useful evidence on the origin of the flicker noise. When making measurements on standard valves, there were encountered a number of defects which lead to the generation of excess noise at low frequencies.