| 摘要 |
RF DRIVE CIRCUIT FOR AN ION PROJECTION PRINTING HEAD In order to drive the RF lines (electrodes) of an ion projection printing head or cartridge, driver circuits are provided which generate high voltage, radio frequency signals with rapid envelope rise and fall times so that dots of varying density in accordance with a gray scale may be formed on a rapidly moving dielectric surface. A separate RF driver circuit for each line includes an active switching device, preferably an FET. A series resonant circuit is connected across the active device. This circuit is provided by an inductor connected in series with the effective capacitance presented by the RF electrode of the ion projection head which is being driven. The inductor and effective capacitance defines a series resonant circuit. The active device is driven via a pulse amplifier by pulses repetitive at the RF rate and the active device is connected to a power supply, preferably through a parallel resonant circuit which broadens the frequency response characteristic (flattens the effective resonance peak as measured across the RF electrode), so that the current switched through the device is of sufficient magnitude to develop a peak-to-peak voltage across the effective capacitance of the RF electrode of the head to provide sufficiently high peak-to-peak voltage RF cycles. These cycles may be gated so as to develop ion dots on the dielectric surface having the required gray scale gradiation; the magnitude of the ion charge and the gray scale depending upon the number of cycles of the RF drive voltage used while projecting ions onto the dielectric surface. PR-8924
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