use of decouple caps
Hi !!!
To answer to laststep, I think the ESR of a cap is mainly related to the package.
So a 1pF cap has quite the same ESR of a 10pF cap.
So when you put 10x 1pF Cap in parrallel to obtain the same value of 10pF cap, you will have the ESR divided by 10....
everybody would like to use a perfect cap with high value, small package and perfect response. But it doesn't exist. We only have some cap which are good, but for a limited region (value, size, high frequency response, precision, temperature, or piezo-electric response...).
So we use several cap, each one are good in a limited region, but the combination is good for a wider range...