(1) The condition existing in any circuit in which an increase in the input signal produces no further change in the output [13]. (2) The operating point of a vacuum tube or transistor at which a further increase in grid or base current no longer produces an increase in plate or collector current [6] [7]. (3) In a magnetic core, the condition in which a magnetic material has reached a maximum flux density and the permeability has decreased to a value of (approximately) 1 [8].