Looking for a circuit to turn off normally on negative 500 volts with logic high TTL. The negative voltage would be normally on with TTL low or with no control signal being applied. A high TTL would turn off the negative voltage (off period will be perhaps 100 microseconds). The negative voltage is applied to plates in a vacuum so very little or no current draw. Turn off/on times of tens of microseconds. It would be ok to use a battery for bias if necessary.
Steve