Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1982-03-29
1984-04-10
Martin, John C.
Facsimile and static presentation processing
Facsimile
Recording apparatus
358172, H04N 568, H04N 518
Patent
active
044424582
ABSTRACT:
The drive circuit of the present invention is characterized by a second amplifier for amplifying the video signal which controls the voltage at the control grid G.sub.1 of the cathode-ray tube. This second amplifier has a wider bandwidth than the similar amplifiers of the prior art. It therefore generates a signal having a lower dynamic range than the dynamic ranges of the output signals associated with the similar amplifiers of the prior art. To compensate for the lower dynamic range of the output signal generated by the second amplifier, the drive circuit of the present invention measures the current in the cathode of the cathode-ray tube, converts this measured current into a voltage, stores the voltage in a capacitance, and amplifies the stored voltage in a fourth amplifier. The fourth amplifier generates a signal having a wider dynamic range than the dynamic range of second amplifier. The output of the fourth amplifier is combined with the output of the second amplifier. Consequently, the DC signal from the fourth amplifier is added to the AC signal from the second amplifier. The dynamic range of the signal from the fourth amplifier is therefore added to the dynamic range of the output signal from the second amplifier. The resultant signal energizes the grid G.sub.1 of the cathode-ray tube. The video amplifier of the present invention therefore has a wider bandwidth than prior art video amplifiers while retaining a relatively wide dynamic range of the signal energizing the control grid G.sub.1.
REFERENCES:
patent: 3598913 (1971-08-01), Janssen
patent: 4200882 (1980-04-01), Janssen
patent: 4224640 (1980-09-01), Hovens et al.
Conrac 6000 Series Monitor, Video Amplifier Board Schematic, Nov. 12, 1976.
Martin John C.
Peng John K.
Tektronix Inc.
Winkelman John D.
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