A mosfet, a diff. comparator, a bridge rectifier, and an inductor walk into a bar where they talk to a BC557 and a BC547 a big cap and some resistors.
What would you call this thing? I don't remember building it. My guess from the fact it has 4 leads two are "AC" and one is cat. and an. that it's a regulator or tiny power supply.
Will it mess it up if I put DC to it? How would I know how much voltage it takes? It has no part numbers on the board. Certainly it can't take mains power could it? Why else would you have A/C inputs unless it's supposed to work with a transformer.
What does the comparator do? I haven't seen that in a power supply. Is it so it can adjust a range of voltages and still stay at the output? To find voltage do you look at how much this IC can handle then trace out resistor that goes to it?