this is the basic circuit i will want to use (at the bottom)...obviously the part values still have to be given, but can the supply voltage be changed to a negative voltage (so i can yield a positive voltage at the output) without changing the components? like for the positive input version, there is a N-channel mosfet...does the negative input version need a P-channel mosfet and all the capacitor polarities reversed? the diagram i am talking about is on page 14

http://techtrain.microchip.com/webseminars/documents/IntroToSMPS_031809.pdf