Vertical Mode Selection With Selectable "S" Correction
Original Publication Date: 1988-Sep-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a circuit for use on visual 110o CRT monitors that control "S" distortion in vertical scan coils over a range of display formats without affecting other electrical parameters. The "S" correction of vertical ramp generator circuits in displays is usually achieved by boosting the gain of the amplifier at the fundamental frequency while maintaining the original phase. This is usually achieved as a byproduct of AC coupling the deflection yoke which introduces a low frequency roll off. To overcome this, frequency-dependent AC feedback, and the effect of carefully chosen time constants in the DC feedback path, can be combined to produce a slight resonance at the fundamental frequency which, in turn, causes the characteristic's "S" correction (Fig 1).