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Phil Allison
Guest
"Jeff Liebermann"
"Phil Allison"
** I see no such trend for the electros.
The ESR of most electros is almost constant down to about 500Hz, then rises
to a few times its high frequency value at 50Hz. I believe mobility of the
ions in the electrolyte is the cause.
Electros uniquely have very low Q factors - which means their impedance *
stays low * over a very wide frequency range.
A typical 470uF electro has an impedance under 0.1 ohms from 4kHz to 1MHz as
does the 330uF example in the graphs.
High Q capacitors ( film and ceramic) all have sharp impedance dips at self
resonance.
..... Phil
"Phil Allison"
That link shows ESR curves with frequency of a couple of * CERAMIC *
capacitors of unusually high values.
Oops, y'er right. Sorry(tm).
Oddly, while the ESR of the ceramic caps are much lower than
electrolytics, the curve shapes seem to be similar.
Googling, I find:
http://www.low-esr.com/esrfreqperfcurves.asp
Note the dip in ESR and loss tangent at around 100KHz on various
graphs.
** I see no such trend for the electros.
The ESR of most electros is almost constant down to about 500Hz, then rises
to a few times its high frequency value at 50Hz. I believe mobility of the
ions in the electrolyte is the cause.
Electros uniquely have very low Q factors - which means their impedance *
stays low * over a very wide frequency range.
A typical 470uF electro has an impedance under 0.1 ohms from 4kHz to 1MHz as
does the 330uF example in the graphs.
High Q capacitors ( film and ceramic) all have sharp impedance dips at self
resonance.
..... Phil