or any type of capacitor
on analog circuits or digital?
i think analog shuld be more clean from noises, and on digital there is not a lot to do because the pulses change fast. correct me if i'm wrong and please explain.
On power supplies.
LarryD:
On power supplies.
AC or DC?
This is the best reference I've found to explain why decoupling capacitors are used, how to place them on a PCB and how to select the values: LearnEMC - Electromagnetic Compatibility (EMC) Design Guidelines
Bulk capacitance is all about supplying current changes that are too fast for the
voltage regulator to respond to, but much slower than logic signals. This is usually
the range from 50kH to 10MHz or so. The 10+MHz range is handled by ceramic
caps right close to the load, the lower frequencies by "bulk" capacitance somewhere
on the same pcb, usually electrolytic from 10uF to 500uF typically, depending on
the nature of the current fluctuations.
The feedback loop in the regulator should start kicking in from about 1MHz down,
typically, and should have 50kHz fluctuations well controlled.
When there is a big step change in current in some load (perhaps an LED strip?)
then initially the ceramic decoupling capacitors help fill the gap, during the first
few tens of ns. By then the bulk capacitance starts to notice the power rail drooping
and will take over (the speed of response mainly limited by the inductance between
load and cap). The feedback loop in the regulator starts to repond on a timescale of
a few us, gradually restoring the droop in the power rail and recharging all the caps.
So you will always get a change in the supply voltage due to current fluctuations, but
the various capacitors and regulator act to reduce the severity, and at different
timescales.
Analog circuits are more fussy, but usually don't have fast step changes in current,
so bulk decoupling may be more or less important than digital, the fast ceramic
capacitors may not be useful.
DC power supplies require decoupling.
So do your I.C.s
http://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf
just read MarkT's contribution to this thread
very well explained and a 100% correct.
and, yes, I do appreciate persons who try to explain things in their own words instead of giving you urls/links.