I was reading an app note - http://www.ti.com/lit/an/scaa048/scaa048.pdf
On page 4, the 3db cut off formula is Z/2*pi*L, isn't it just 1/2*pi*L?
Can some one please explain/show how it is Z/2*pi*L, and not just 1/2*pi*L
The cutoff in this case is the point where the series impedance of the power supply is such that the ringing is still "just fine". That is why it is the relationship between two impedances. As frequency goes up, the series frequency of the power supply goes up and a bypass capacitor is needed to avoid ringing
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