I am in need of a stable 5v source, max current around 200mA for a pocket oscilloscope. I have tried a powerbank, but the step-up converter puts through too much ripple that messes with the Scope.
One option would be an LC filter between the powerbank and the scope to cut the ripple. Another would be a 9V battery with a 7805 circuit to regulate down to 5v instead of the powerbank.
My question is, am I right in thinking that the 7805 is the better solution?