EDN have an interesting (for novices like myself!) guide on testing a power supply's design, in which they suggest a 500MHz oscilloscope as one piece of equipment necessary for "proper" testing:
The test equipment needed for proper power supply testing varies with the type of power system being tested, as well as the financial budget for the equipment. Here is an example list of equipment:
- Oscilloscope 500 MHz BW or greater with probe for noise measurements.
It seems a random choice, except that it is among the very highest spec'd oscilloscope I've seen on the market.
Are they trying to say you should go for the best your budget can stretch to, or is there some technical reason why 500MHz is the magic number?
I'm guessing it might be related to typical SMPS frequencies, PCB and other parasitics, and other characteristics of current technologies, or some artifact of the nature of EMC?
Firstly it bothers me it's seemingly been plucked out if thin air. And it's weird that the article seems to be written for informing readers of sub-professional level, yet recommending top-end equipment (totalling a near 6 figure sum).
Can someone make sense of this? If that's too vague a question, then simply, why 500MHz? Maybe it's just the one sitting in front of him.