Re: Pulse transformers, why?
- From: Rich Grise <richgrise@xxxxxxxxxxx>
- Date: Fri, 07 Apr 2006 21:51:01 GMT
On Fri, 07 Apr 2006 03:15:05 +0700, ErikBaluba wrote:
Hi,
I'm putting together my own SPI based LAN interface using a cheap Microchip
ethernet chip.
Why are circuits interfaced to Ethernet have pulse transformers? What make
such transformers special? I saw one example schematic for a
pulsetransformer were it was grounded via 2000V capacitors. Is data
transmitted on an Ethernet's twisted-pair cables by generating high voltage
pulses to facilitate longer distance and higher speed because of increased
S/N or something? I tried to find voltage specs for Ethernet signals on
google but couldn't find any.
And then what about such transformers used on the phone lines? I figure they
are necessary to step down the "high" phone line voltages?
They're called "pulse transformers" to distinguish them from all of the
other varieties of transformers - here's an interesting read:
http://en.wikipedia.org/wiki/Line_transformer
From my own learnings/experience, I'm speculating that they use pulsetransformers because of their excellent rise-time characteristics, which
would translate into frequency response, and they also can handle enough
power to put a good, solid, reliable signal on the line, plus I intuit
that they have good noise immunity on the receive side, so to speak.
Hope This Helps! (Feh - hope it's accurate! :-) )
Rich
.
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