[SI-LIST] Re: Question regarding current loop
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Doug Brooks" <doug@xxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Mon, 24 Apr 2006 14:05:28 -0700
As always current is an effect, not a cause. The cause is EM fields
travelling independently on two transmission line each of which has a plane
as a partner. The current for each is flowing in the plane. That these
currrents happen to be equal an opposite is incidental.
To help understand this, look at an Infiniband cable. It is two
completerly independed coaxial cables, neither of which knows the other
exists nor cares.
> [Original Message]
> From: Doug Brooks <doug@xxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 4/24/2006 12:39:58 PM
> Subject: [SI-LIST] Question regarding current loop
>
> Assume we have a differential pair, driven in odd mode with no timing
offsets.
> Assume the pair is terminated with a single resistor between the two
traces.
> Assume the signal is purely trapezoidal.
> Assume there is an underlying plane (but assume what you want about the
> spacing to the plane.)
> Assume what you want about the spacing between the traces.
> *If* current flows in a closed loop and *if* current is constant
everywhere
> in the loop, and *if* current is a point (as opposed to an average)
concept
> in time....
>
> What is the definition of the current loop at the instant when the
current
> wave form is at the middle of the constant part of the wave form (between
> the rise and fall times)?
>
> Doug Brooks
>
>
____________________________________________________________________________
-
> Check out UltraCAD's differential impedance and skin effect calculators
at
> http://www.ultracad.com
>
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