[SI-LIST] : [SI-LIST] Positive ECL (PECL) voltage swings, but designed to be

Salvador Aguinaga (Salvador_Aguinaga@mw.3com.com)
Thu, 29 Jul 1999 11:28:21 -0500

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All,

Will some one shed some light on why differential lines (to and from) a ECL
device are AC coupled? I've been unsuccessful at finding an answer from my
internet searches.

I am speaking specifically to the AC coupling that is found in fibre-channel
ser-des transmitters.

(P)ECL C1
|\-------------o-----||---
| \ |
| / | C2
|/o------o-----------||---
| |
| |
< R1 >R2
> <
| |
| |
_|_ _|_
GND GND

Where C1=C1=0.01uF

Why is the capacitor needed? What is the theory behind this implementation?

Thanks,

--------------------------------------------------------
_ __ Salvador Aguinaga Jr.
/_/ )/ _| Carrier Systems Group
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=B7 R&D
__ |( (_ _ _ Mt. Prospect, Illinois
\ \_)\__|(_)|)) (847) 222=B72833

=

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