The magnetic amplifier (sometimes calle a self-saturated amplifier) is a magnetic device consisting of a saturable reactor (transformer) modulated by a direct current. This DC current is introduced in the primary winding of an iron-core transformer and used to control the AC current in the secondary winding by saturating the core with magnetic flux. As the DC in the primary winding is increased, the output AC current and load voltage in the secondary are increased by varying the impedance of the secondary winding through inductive reactance.