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

[Adam S]

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.

 

[Phil Allison]

"Adam S"

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 ?

** Murata don't think so:

http://www.mouser.com/catalog/628/631.pdf


Any day you can avoid using a tantalum cap is a good day.




........ Phil

 

[Joe G \(Home\)]

Why dont you put some "accurate" spice models of the manufacturers capcitors
in to a Spice simulator and see how they react to transient and frequency
inputs.

Here! Yageo have the spice models and simulator.
http://www.yageo.com/?mid=40029

JG

 

[Ancient_Hacker]

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.

 

[Phil Allison]

"Ancient_Hacker"

"above resonances"? A capacitor is an inductor above resonance, so
any plots up there are rather useless.

** Complete bollocks.

Also misleading, as the
resonant frequency is going to be different in your circuit than in any
other, or test, circuit.

** The ( series) resonant frequency shown is that of the cap alone -
fuckwit

I'd make up a little test jig,

** You can do a little jig on your head for all anyone here cares.



....... Phil

 

[Joel Kolstad]

"above resonances"? A capacitor is an inductor above resonance, so
any plots up there are rather useless.

Not so... in many cases operating capacitors above their self-resonant
frequency is useful.

Also misleading, as the
resonant frequency is going to be different in your circuit than in any
other, or test, circuit.

This is true for pretty much any simulation vs. a built-up PCB; the devil is
always in how much the difference is.

 

[Ancient_Hacker]

Joel Kolstad wrote:

Not so... in many cases operating capacitors above their self-resonant
frequency is useful.

Pls answer these questions:

(1) In a series LC circuit, below resonance the reactance is: (
capacitive, resistive, inductive )

(2) At resonance the reactance is: ( capacitive, resistive, inductive
)

(3) At above resonance the reactance is: ( capacitive, resistive,
inductive )

(4) If you want a capacitor, use a ( capacitor, resistor, inductor )

(5) If you use an inductor in place of a capacitor, you are a:
(winner, drone, loser )

 

[Fred Bartoli]

Ancient_Hacker a écrit :

Joel Kolstad wrote:



Pls answer these questions:

(1) In a series LC circuit, below resonance the reactance is: (
capacitive, resistive, inductive )

(2) At resonance the reactance is: ( capacitive, resistive, inductive
)

(3) At above resonance the reactance is: ( capacitive, resistive,
inductive )

(4) If you want a capacitor, use a ( capacitor, resistor, inductor )

(5) If you use an inductor in place of a capacitor, you are a:
(winner, drone, loser )

The obvious answer being to use an inductor above its SFR

 

[Don Lancaster]

Ancient_Hacker a écrit :


The obvious answer being to use an inductor above its SFR

Uh, won't there be the slightest amount of leakage at dc?

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Ancient_Hacker]

The obvious answer being to use an inductor above its SFR

Haw!

Actually, I glommed onto a bunch of "Genoformers" which curiously
measured as capacitors on my LC bridge at 1000 Hz. Turned out they
were transformers designed to pass seismic signals, so 1000Hz was way
above their SRF.

 

[Joel Kolstad]

Pls answer these questions:

(4) If you want a capacitor, use a ( capacitor, resistor, inductor )

Capacitor. However, once you get past EE 101 designs, you find that there are
plenty of cases where you can't get a single capacitor that behaves reasonably
close to an ideal capacitor over the design's intended operating range.

(5) If you use an inductor in place of a capacitor, you are a:
(winner, drone, loser )

Having to with deal with the reality of doing more complex designs than you
do?

Interested in testing out a gyrator?

 

[PeteS]

Capacitor. However, once you get past EE 101 designs, you find that there are
plenty of cases where you can't get a single capacitor that behaves reasonably
close to an ideal capacitor over the design's intended operating range.

Hear hear.

I had to do a very systematic approach to a number of InfiniBand boards
I designed. Without going into detail, let's just say there were a
_lot_ of frequencies of interest that had to be appropriately
decoupled.

No one size or type of cap will span the decoupling requirements on a
reasonably complex board; one chooses various caps to implement
specific parts of the decoupling requirements. I also used some
inductors, of course - there are times for them; and all that doesn't
incude the power system


Cheers

PeteS

 

[Phil Allison]

"Ancient_Hacker"


( snip all the asinine drivel)


???????????




......... Phil

 

[Genome]

Cheers

PeteS

Have you bonked Lyn(n) yet?

DNA

 

[Fred Bartoli]

Don Lancaster a écrit :

Uh, won't there be the slightest amount of leakage at dc?

I won't call that leakage, but I think I added a smiley
Here's another one