A power source for the operation of a deflection coil for an electron beam of an x-ray tube has a voltage source and a bridge circuit that is connected with each end of the deflection coil, respectively via one power switch in series connection to opposite poles of the voltage source. A current tap taps a coil current signal proportional to the current through the deflection coil. An activation comparator and a deactivation comparator are connected with the current tap to which an activation current signal I.sub.min and a deactivation current signal I.sub.max are supplied. The power switches are connected with the activation comparator and deactivation comparator such that they are closed in the event that the coil current signal undershoots the activation current signal I.sub.min and opened in the event that the coil current signal overshoots the deactivation current signal I.sub.max.