I've recently run into a number of consumer-grade devices that use 50v, 0.22uF electrolytic capacitors, as well as other similarly rated parts, all below about 10uF. In use, the voltages on them are far less than the rating, usually around ~15-25V maximum, and they seem to be used in op-amp filters or as rail bypass caps.
My question is this: Why on earth would you ever want to use an electrolytic in that kind of a situation? I get that ceramics de-rate as the voltage increases, but surely a 1uF 50-250V ceramic would be better for device lifetime and would be cheaper to boot?
(And yes, I have read Ceramic caps vs electrolytic. What are the tangible differences in use?, but it doesn't quite answer my question.)
Best Answer
Both of your examples commonly care about ESL and ESR of a capacitor. Along with many other examples like LDO output stability etc. I have done designs like this using Tantalum instead of ceramics for the exact reason. Stuff from China will most likely use Electrolytic ones to save money.
There are still applications where the higher ESL and ESR of an Electrolytic capacitor is hard to replicate.
An incomplete list of applications that still may prefer Electrolytic or Tantalum over Ceramics