A control circuit for controlling an electron-emitting device is formed to draw, with a voltage applied, an excitation current being related to a number of electrons emitted. The inventive control circuit includes a first determinator for determining whether an amount of charge transported by the excitation current has reached a predetermined charge threshold value, a second determinator for determining whether a magnitude of the excitation current has reached a predetermined current threshold value, and a switch for switching off the excitation current as soon as the first determinator determines that the amount of charge has reached a predetermined charge threshold value, or as soon as the second determinator determines that the magnitude of the excitation current is smaller than the predetermined current threshold value. The control circuit allows the usage of, for example, CNT arrays for irradiation and operates on the basis of the current drawn by the electron-emitting device, which makes possible a simple setup.