A dissipator useful for discharging provides a continuously variable high-voltage load under control of a computer or other device capable of providing an analog control voltage. Known dissipator arrangements use multiple high voltage switches and resistors to attempt to dissipate power. However, the disclosed dissipator uses the resistive property of a matrix of photo resistive cells, typically cadmium sulphide arranged on a circuit board. These photo resistive cells are series connected and controlled optically to vary their resistances. An optical control signal is provided for each photo resistive cell by a corresponding light emitting diode (LED). The amount of light emitted by each LED is analog controlled.