Saturation current

(electronics) In general, the maximum current which can be obtained under certain conditions. In a vacuum tube, the space-charge-limited current, such that further increase in filament temperature produces no specific increase in anode current. In a vacuum tube, the temperature-limited current, such that a further increase in anode-cathode potential difference produces only a relatively small increase in current. In a gaseous-discharge device, the maximum current which can be obtained for a given mode of discharge. In a semiconductor, the maximum current which just precedes a change in conduction mode.
(nucleonics) The ionization current in a gas tube when the applied potential is large enough to collect all ions produced by ionizing radiation.

A term having a variety of specific applications but generally meaning the maximum current which can be obtained under certain conditions.

In a simple two-element vacuum tube, it refers to either the space-charge-limited current on one hand or the temperature-limited current on the other. In the first case, further increase in filament temperature produces no significant increase in anode current, whereas in the latter a further increase in voltage produces only a relatively small increase in current. See also Vacuum tube.

In a gaseous-discharge device, the saturation current is the maximum current which can be obtained for a given mode of discharge. Attempts to increase the current result in a different type of discharge. See also Electrical conduction in gases.

A third case is that of a semiconductor. Here again the saturation current is that maximum current which just precedes a change in conduction mode. See also Semiconductor.

The maximum current in a roentgenray tube that fully uses all electrons that are available at the cathode for the production of roentgen rays.

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