It is amazing when we realize that everything is done using a power supply of 3v. Do they do this using normal transistors or are there some super low power transistors available???
Most propable, they use a step-up DC to DC converter.
This is extensively used in all Mobile phones (GSM) and in general portable equipment.
I cannot see why the cameras are exeptions.
Anyway, if you consider that a Pentium4 CPU uses voltages as low as 1volt then there is no problem for a digital camera to go so low (3v)