This circuit operates exactly as the 555 ignition coil driver circuit. The only difference is the frequency is much greater. This is accomplished by adding a smaller value timing capacitor to the 555 circuit. From a 12 volt power supply this circuit can generate up to 9kV. The flyback that I used was one of the cylindrical types (not good). But it still worked well because it was quite large. Keep in mind that the output of a cylindrical flyback is half wave rectified ("raw" direct current). This driver works well but the maximum arc length that you will draw off of it with a 12v supply will be about 1.5cm, even with a flyback with a disk shaped secondary. For a better design and higher voltage go to my single transistor flyback driver page.