Circuitry for the positioning of the electron beam in CRT display systems such as exemplified by the M. S. Granberg, et al., U.S. Pat. Nos. 3,434,135 and 3,489,946 includes X and Y deflection coil current drive systems of various designs. These prior art systems include digital logic that selectively switches in or out constant current sources of individually fixed but separately different incremental current magnitudes or levels such that the desired deflection-determining current level is caused to flow through the X (and Y) deflection coil.
In CRT display systems, the cathode ray tube face is usually a flat surface. Equal increments of deflection-determining current move the electron beam along the face in increasing incremental lengths for increasing distances away from the center of the face producing a distortion called the "pin-cushion" or "non-linear effect." Prior art CRT display systems have included various correction features to compensate for such distortion. Aslo included were constant current drivers and electronic switches to maintain fixed increments of deflection-determining current and to prevent switching induced transients that further distort the display. The present invention is directed toward a CRT display system that eliminates these above noted causes of display distortion.