I have a HP laptop power supply 18.5V/3.5A that I intend to connect directly to LM7812 or LM7805 voltage regulator when I need to drop the voltage to 12V/5V. Since the laptop power supply (which is switched mode I assume) should be outputting a filtered voltage to the LM7812...are the input/output capacitors recommended in the datasheets truly necessary? could the LM7812 work in this particular case..without capacitors? what would be the disadvantage? I do have a couple of generic DC-DC Buck converter boards off ebay and these work, but am utilizing it for other purposes.