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Simple Dynamic Focusing Circuit for Display Monitor

IP.com Disclosure Number: IPCOM000036630D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Ohsawa, T: AUTHOR [+2]

Abstract

Disclosed is a dynamic focusing circuit which does not require high- voltage device components to mix horizontal focus waveform and vertical focus waveform by a current mixing method. The amplitude of each dynamic voltage, horizontal or vertical focus voltage, can be set independently, and can be changed instantly by an additional transistor switch to fit a multi-mode display monitor.

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Simple Dynamic Focusing Circuit for Display Monitor

Disclosed is a dynamic focusing circuit which does not require high- voltage device components to mix horizontal focus waveform and vertical focus waveform by a current mixing method. The amplitude of each dynamic voltage, horizontal or vertical focus voltage, can be set independently, and can be changed instantly by an additional transistor switch to fit a multi-mode display monitor.

Fig. 1 shows a simple dynamic focusing circuit. This circuit can be separated functionally into two stages which are an amplifying stage and a current-to- voltage conversion stage. The amplifying stage comprises a couple of common- emitter transistors Q2 and Q3, which amplify horizontal parabolic waveform and vertical parabolic waveform individually. Collectors of both transistors are tied and are connected to an emitter of a high voltage transistor Q1 which is in the current-to-voltage conversion stage. The distinctive uniqueness of the circuit disclosed here is a mixing process of two amplified parabolic waveforms. The process is done before a current-to-voltage conversion and brings mixed current waveform at the emitter of the transistor Q1. The large dynamic voltage appears finally at a collector of transistor Q1 by a high voltage gain of common-base amplifier. Only by this, the mixture of two focusing voltages can be attained, and no additional high-voltage device component is necessary for mixing purpose.

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