I want to test the op amp's noise (up to 10MHz), the output of the op amp is ac coupled by
a capacitor. What kind of capacitor should I choose? aluminum electrolytic?
tantalum? or ceramic? Aluminum electrolytic doesn't have good high frequence characteristic. ceramic could dishape the signal. For tantalum, it has polarity, so in which way should I connect it?[/img]
Use 2 capacitors connected in parallel: one electrolytic (can be bipolar) and the other ceramic.
This combination will cover wide frequency spectrum ..
Regards,
IanP
Capacitors can cause noise with DC bias. Let your circuit sit for a long time before measuring it. NPO ceramic and mica and plastic dielectric types have the best performance in this area.