Difference between De-Coupling and Bypass Capacitor

[v_kumar]

Hell All,
Can any one provide some domentation evidence which provides proper differenctiation between Bypass and Decoupling capacitors.

thank you
Kumar

 

[srizbf]

a 'bypass' capacitor has the characteristics in the name itself.
a bypass cap will bypass the current.

eg. bjt emitter resistor with bypass capacitor.
the cap will bypass the current at ac frequencies (preventing pass through the resistor) so that it provide an almost short to ground at emitter point.

a 'decoupling' cap will decouple the node concerned .
the decoupling cap at power + node to gnd will provide a zero impedance for high freq. but not at dc.

srizbf
19thmay2010

 

[c.sundstroem]

Hi,
I had this PDF from www.designers-guide.org on my computer. It might not be suitable as a reference in an academic context but I think that it offers a good explanation of the difference between decoupling and bypassing.