Dynamic focus system for CRT display

摘要

A dynamic focus sustem for CRT display processes horizontal and vertical rate signals derived from the horizontal and vertical deflection systems of the CRT display. The output signal is processed in part by a common base amplifier and an interactively coupled boot-strapped emitter follower to substantially increase signal handling capability. A diode clamp network is simultaneously driven by composite horizontal and vertical rate dynamic focus signals as well as a DC static voltage and vertical rate parabolic signal to facilitate easy adjustment and setup of the CRT display. The vertical parabolic signal is derived by a single amplifier stage simultaneously driven by vertical deflection and vertical yoke signals. The horizontal parabola amplifier is operated class B to minimize device power and supply voltage needed, and the common base operation of the horizontal amplifier permits the use of lower voltage devices. The composite horizontal and vertical signal and the vertical rate parabolic signal are separately capacitor coupled to the diode clamp to minimize device power and required supply voltage in their respective amplifier circuits.