[SI-LIST] Re: inductance of differential stripline

  • From: "Joe Paul" <joepaulm@xxxxxxxxxxxxx>
  • To: "istvan.novak@xxxxxxx": ;;, si-list@xxxxxxxxxxxxx
  • Date: Tue, 8 Feb 2005 12:12:32 +0550

Sir,

Excuse me and Correct me if I am wrong

I feel that the inductance of the differential line measured by applying a 
differential signal on a 
pair of differential traces, will be less than the twice the inductance 
measured by applying a 
single ended signal on a trace , as the magnetic field formed due to current in 
one traces aiding 
the current flow other.

i.e differential inductance will be, equlaent to 2 single ended inductances in 
series and their 
mutual inductance between them in parallel.

I don't know about the accuracy the tool Iused , but Inductance calculated 
shows that the mutual 
inductance are not that small to be ignored.
(as per Inductance calculator at http://emcsun.ece.umr.edu/new-induct/  )

My assumptions are 
* Single ended inductance measured with no other lines in its vicinity.
* Differential inductance  measured with no other lines other than them.



Joe
Ordyn,India.

> Mark,
> 
> Welome to the si-list forum.
> 
> In a very simplistic way we can say that the differential impedance
> is twice the single-ended impedance because we connect two
>  transmission lines in series.  Series impedances add, similarly
> series-connected inductances add.  You can use the same
> formula of Zo*delay, just have to substitute the correct terms: 
> differential impedance and differential (odd-mode) delay.  
> You can find very good tutorials on the subject on the TDA
> Systems website. http://www.tdasystems.com/
> 
> Regards,
> 
> Istvan Novak
> SUN Microsystems
> 
> Mark Burford wrote:
> 
> >Hi guys, just subscribed.
> >I understand the inductance of stripline to be Z0*delay_of_line
> >Could anyone tell me what the inductance is for differential odd mode
> >stripline please?  Does it change? I know Z0 for differential stripline
> >is near double that of single stripline, but does this affect
> >inductance?
> >
> >Many thanks
> >
> >Mark Burford
> >Mburford AT xyratex DOT com
> >
> >
> >  
> >
> 
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