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Hi all, how do I know what is the maximum frequency that a particular capacitor can handle? Some datasheets I came across don't specify this thing. I need to find capacitors that will be able to work up to 5GHz. Thanks.
Usually the working limit of a capacitor is SRF (Series Resonant Frequency). Before that point the reactance of the capacitor is pure capacitive, and after SRF the reactance is inductive.
In some particular applications capacitors are used only at SRF where the equivalent impedance is minimum.
Capacitor manufacturers have come up with super high dielectric constant ceramics, and are able to cram a lot of capaciatance into a very small footprint. That may be fine if you are trying to stabilitze an op amp, but may be a disaster at 5 GHz. The L x W are large enough for the high ξr that the capacitor will form a rectangular resonator. When this happens, strange things occur, like a series open circuit!
So one key is to stay away from big capacitance values. A 10,000 pF capacitor is more likely than a 1000 pf capacitor wich is more likely than a 22 pF capaciator to resonate. So only use as much capacitance as you need in series applications. In shunt applications where you need to quell low frequency oscillations, use two or more capacitors in parallel to ground, such as a 100 pF parallel with a 10,000 pF.