Abstract: A flux cancelling transformer line circuit includes an AC current source that blocks AC current and passes DC current. The current source is connected between the primary and secondary windings of a transformer. Direct current flowing through the primary winding generates a magnetic flux. The current source passes the direct current to the secondary winding self-cancelling the DC flux created in the primary winding. Since DC current is coupled from the primary windings directly into the secondary windings, the same DC current flows in both windings. Thus, DC flux is precisely cancelled in the transformer. The current source includes a transistor, which is biased in a low impedance linear region by the DC signal and a capacitor that operates the transistor in a high AC impedance condition.