How small can I make a transformer and still get 1:30 or preferably higher step-up ratio ? I have been reading alot about transformers and I know using higher frequency will reduce the size, and I need to use ferrite core for high frequency. I don't want to use really high frequency, probably up to 2Mhz. The size limit is 0.5 cm2, input voltage is 6-10v from button cell batteries. What shape core should I use and what kind of winding scheme?