One shot pulse generator and logic level converter circuit

摘要

An intensity control system for a cathode ray tube (CRT) is disclosed. The system provides precise intensity control for a CRT whose control characteristics are only slowly varying. Precise intensity control is provided by measuring the cathode ray tube beam current. The beam current is set at a desired value without producing an image on the tube face. Thus, tube intensity can be set without fogging photoresponsive media which is in position for exposure by images on the cathode ray tube screen. The intensity may be set to a value determined by a manually adjustable intensity control. The intensity is preferably set by iterative threshold comparison of the actual beam current with the value corresponding to the setting of the intensity control. A unique threshold comparison circuit provides precise comparison between the reference level set by the intensity control and the actual beam current.