Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Patent
1984-01-19
1985-12-24
Blum, Theodore M.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
H01J 2958
Patent
active
045609101
ABSTRACT:
A dynamic focusing circuit for a CRT includes a DC coupled parabolic voltage waveform generator having a first capacitor supplied with constant charging current from a transistor for developing a sawtooth voltage waveform thereacross, a first switch transistor for discharging the first capacitor at a horizontal frequency rate, a second capacitor DC coupled to the first capacitor through a voltage-to-current generator transistor for developing a parabolic voltage waveform thereacross and a second switch transistor for discharging the second capacitor in synchronism with the first capacitor. Tilt and amplifier control transistors are DC coupled to the second capacitor. A vertical rate parabolic correction waveform is also developed by similar circuitry. The upper transistor in a cascode amplifier develops a high voltage replica of both the horizontal and vertical parabolic correction waveform voltages for application to the focus electrode of a CRT. Horizontal and a vertical amplifier transistors are coupled in parallel in the lower portion of the cascode amplifier and are supplied with the corresponding parabolic correction voltages.
REFERENCES:
patent: Re30271 (1980-05-01), Dietz
patent: 3412281 (1968-11-01), Richards, Jr. et al.
patent: 3543080 (1970-11-01), Wuensch
patent: 3784869 (1974-01-01), Takahashi
patent: 3953760 (1976-04-01), Matsuura et al.
Blum Theodore M.
Zenith Electronics Corporation
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