A FERRACTOR amplifier is a type of magnetic amplifier circuit built with Ferractor®s (a type of transformer wound on a saturable core having a nearly rectangular hysteresis loop with two stable states). Univac used them in the logic circuits of some of their computers in the late 1950s and early 1960s instead of vacuum tube or transistor electronic amplifiers.

Ferractor® was a registered trademark of Sperry Rand Corporation.