Can I use a charger that provides the same voltage but a different amperage?
Yes.With a couple of caveats, of course.Getting the right power supply, involves matching voltage, amperage, and polarity. And each have different constraints.
 If you replace the power supply for some reason with one that has a maximum amperage rating that is less than the previous and less than what your device actually requires, then you may end up with a burnt out or (at least) overheating power supply, and the device itself may not function, or may not do so well.
In short, when replacing an external power supply or charger:
1.Make sure that the voltage matches as closely as possible.
2.Make sure that the new supply is rated to provide the same amperage or more.
3.Make sure that the connectors match, both in physical form and in polarity.