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The difference between a decoupling and a bypass capacitor

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sapta

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can anyone explain me the difference between a decoupling and a bypass capacitor please. how do i choose the right value.

sap
 

kishore2k4

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bypass decoupling

Effectively they are both the same. A decoupling capacitor is used to decouple it from other parts of the circuit/sub-circuit like switching transients, voltage droops etc. It is also used to for providing transiet power for that particular circuit.

Other than this it also serves the role of a bypass(capacitor/network) which essentially shorts the high frequency/unwated signals in the DC power line.

http://www.hottconsultants.com/techtips/decoupling.html A good read
 

laglead

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bypass decoupling difference

It really depends on their posistions, I think.
 

shaikss

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diff between bypass and decoupling

Decoupling capacitor breaks the coupling between a portion of a circuit to ensure proper operation. That is another part of the circuit is unaffected by the changes in one part of the circuit.

Bypass cap allows a low impedence path to shunt transient energy to the ground from the source. it removes the ac component
 

dkace

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differnence between bypass decouple

Ok, I think that everyone has a good point on it, but it would be better if you do the math:

Start with the impedance of the capacitor. Its value is 1/ωC, wich means that it is invercly proportional to the frequency of a signal applied to it! There you are:

Decoupling capacitor of DC : It filters out all the zero frequncies and leaves your power line clean of "dirty" DC components.

Bypass capacitor, is a Decoupling capacitor from other frequencies: In wich part of the circuit are you going to use it? Which is the unwanted frequency components of the signal you want to get rid off? Do the math and you will have the value together with a resistor to act as a bandpass, lowpass or a high pass filter.

I hope it helped a bit ( I had the same problem before figuring that there is nothing more than a math expression to understand the physics behind this terms).

D.
 

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