Re: Can one 1uF ceramic replace a combined 1uF tant + 10nF for bypassing ?


Adam S wrote:
According to most capacitor manufacture datasheets the impedance vs freq
plots of a 1uF X7R vs a 10nF X7R are equal for frequencies above
resonances. So I wonder if there are problems using one large 1uF
ceramic in place of the traditional arrangement of a tantalum in
parallel with a small value ceramic for bypassing purposes ?

Adam.

"above resonances"? A capacitor is an inductor above resonance, so
any plots up there are rather useless. Also misleading, as the
resonant frequency is going to be different in your circuit than in any
other, or test, circuit.

I'd make up a little test jig, with a noisy IC, say a 74F161 toggling
at 50MHz, a HF scope to BNC coax line soldered right to pins 7 and 14,
and various capacitors I can plonk onto those pins.

.

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