The "fan out", or "fan-out" of an
electronic component is a
property indicating the
maximum number of
comparable devices that the
component can
source or
sink current to/from, while the
voltage at the
output still remains at a level that is properly
interpreted as a
logical high or
logical low. In other words, it is a count of the maximum number of devices I can hook up to the output of a component, and still be guaranteed have good
high and
low voltages.
See also TTL.