I have been trying this miniature Tesla coil based on Slayer's exciter circuit (shown below). The part that I don't understand is how this parasitic capacitor exists? I know that for a capacitor there needs to be 2 opposite charges separated by a distance L (which should not be too large as the capacitance becomes negligible). So how do I visualize the capacitor based on these conditions (opposite charges and distance of separation)?
And even assuming that it exists, initially when the switch is turned on voltage is induced on the primary which is reflected on the secondry side charging the capacitor. But after a while since it's only a DC source the induced voltage slowly fades away, but how does the base emitter diode get reverse biased? I have made the circuit and it works even though I did not have the diode shown in the image, but I just want to get it working right! I did see an earlier post similar to this, but it did not really help with my questions.