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What is the bypass capacitor used for voltage regulator?

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newman

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Please tell me........
 

brmadhukar

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Hi,
Capacitor can store voltage and does not allow voltage across it to be changed instantaneously. So when any voltage aconnected across it tends to change drastically, the capacitor proved additional chage and keeps the voltage from changing suddenly. This is a voltage regulator action.
B R M
 

glenjoy

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Maybe not bypass, but better FILTER. The higher the capacitance, the better Q=CV, it can store more charge if the capacitance is HIGHER, problem is when you are using a variable, because when you try to switch to a lower voltage, it will not drop down immediately due to high charge storage capability, so just check the value that it discharges immediately as soon as you lower the voltage.
 

jorgito

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Hello,

In other words.... it reduces the output impedance of the regulator at AC frecuencies. It filters some residual noise form the unregulated supply and helps to improve regulator stability too.
 

barrybear

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Also there is always the possibility that a regulator can osscilate if there is no bypass/decoupling . This is why you will find them on purley dc circitry.

Barrybear
 

samcheetah

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Capacitor can store voltage

this is a misconception! voltage is the difference of potential between two points. it cannot be stored because its just a comparison with respect to a certain reference. niether does it store electricity, current or charge. so what does it store????

ENERGY!!!!!!!!

a capacitor stores energy. the charge is always there, its not like as if a capacitor is a void container with no charges. when the distribution of charges change under the influence of an external electric field, energy is stored as a result.

now for the question. u should refer to the datasheet of the voltage regulator u are using. but generally without these capacitors the regulator tends to oscillate. so its better to connect these capacitors in accordance with the datasheet of the regulator u are using. and it usually a good idea to connect a capacitor across a battery. it helps the battery in performing well before going totally flat

i hope that helps
 

sabari

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Capacitor can store voltage and does not allow voltage across it. So when any voltage disconnected across it, it tends to change drastically, the capacitor provides additional charge and keeps the voltage from changing suddenly.Thus capacitor is used in voltage regulator action.
 

Jack// ani

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Read this and you will understand it all.........
 

dkace

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Some more things about bypass capacitors:
-I agree that energy and not voltage is what the capacitor stores. In order to understand electronics better one must understand the physics behind this little, multicoulored "things" that we solder on a board, or we design in a schematic.

-All electronic devices have a detailed mathematical model to describe ther function. It is not the model that makes the device, but it is just a tool to understand better how it works. In the case of the capacitor we say that bypass capacitor, for instance, is used to filter the dc voltage/current from a circuit. Something was written about impendance. This is correct. How do we express it? We say that if resistor doesn't have any dependancy at all from frequence, Zr=R, that is what ever signal we apply to a resistor, form DC to UHF, the resistance will alwaysbe the same: R->Ohms
But in capacitor things are different; Because capacitor "piles" electrons to its plates, that make it respond different in terms of resistance to the movement of electrons: The bigger the amount of electrons in the plates, the bigger the resistance to the newcomers. On the other hand if electrons move to both directions because of alternating voltage across the capacitor then the resistance depends on how fast these electrons accumulate to its plates; In other words: Zc=1/(ω•C). The parameter ω=2•π•f where f is the frecuence of the alternating voltage. So for f=0, Zc is indefinite that means that there is no chance current pass through it.

I think that I gave you a rugh example on bypass capacitors. I will also post a very-very usefull article on why and how we use bypass capacitors in PCB I found a month ago. I can't do it right now, because I have at work and today is Sunday...

My apologises if I used simplicities on this explanation,
D.
 

dkace

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