Regarding the 1N4002 across the regulator:

I haven't seen this additional part mentioned in any modern regulator datasheets or app notes. As I understand it, the purpose of the diode is to provide a current path from the regulated bus to the input supply capacitor when the supply is disconnected. I have seen this occasionally added to LM7805 circuits.

Question: Do modern linear regulators need this part? Similarly, most linear regulator schematics (esp. LM7805) don't include this part. Is that a significant design oversight when the input side has large capacitors?

- Lee