[SI-LIST] Re: A general question of -48V power supply
- From: "Robert Friedman" <rpf1066@xxxxxxxxxxx>
- To: <yifan@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 25 Jul 2003 10:35:48 -0500
Are you familar with the first type of high speed logic Emitter-Coupled
Logic (ECL)? Someone has wriiten on the SI list that the venerable (old)
Motorola MECL handback is available as a big PDF file and it addresses this
subject Due to the topology of the outputs it was advantageous to use a
sizeable ground plane as the highest positive voltage and use a negative
power supply. Overall noise due to current transients were reduced. Also
with a voltage difference greater than +5 Volts it is easier to lower S/N
ratios and run BJTs faster The DC offest is no problem with AC coupling of
course. Now this power supply configuration is legacy and this is old stuff
back in 17970's disco days and before.
Robert Friedman
----- Original Message -----
From: "ÒË·«" <yifan@xxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Thursday, July 24, 2003 8:58 PM
Subject: [SI-LIST] A general question of -48V power supply
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> Is there anybody know why using -48V instead of +48V power supply on =
> backplane in telecommunication field? Except traditional style, any =
> other sepcial consideration?
> =20
>
> Regards
>
> Beck =20
>
>
>
>
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