dB and Differential Pairs?????? 1

[jobeth]

I am trying to understand in better depth what the meaning of dB and differential pairs are? Can anyone provide some insight? Thank you in advance. Bill B.

William H. Bernhart, P.E.


I work as a development engineer for AMP - Tyco Electronics located near Harrisburg, PA. I help design interconnections and electrical connectors for aerospace applications.

 

[IRstuff]

Are you asking if they are related?

A differential pair is a common emitter/source configuration where the emitter resistor is shared, but the load resistors are separate. This is the basis for operational amplifiers and comparators.

dB (decibel) is 10*log(p1/p2) or 20*log(v1/v2)

TTFN

 

[Egress]

Comment on IRstuff respones.

Given that Jobeth is working on connectors I would think
that the reference to differential pairs would relate to
wiring topology for a balanced transmission (signal) line.

My guess is that Jobeth has been given performance criteria
of a connector wich will be used for at least 1 balanced signal line which must have some minimum attenuation (in dB) at a particular frequency or bandwidth.

I must say Jobeth that if you go back through your notes
from Engineering Physics & Electrical principals you will probably find you coverd the basics of the dB. Given that you are one of those Mechanical people we can excuse you
for not paying too much attention at the time.

I've run out of time today, but I'll cobble together a
basic explination of the principals behind balanced/diferential signal lines in a day or so.

 

[IRstuff]

Oh, I assumed that he was looking beyond cables, but if that's the case, EIA/TIA-422 and EIA/TIA-485 would most likely be the standards for twisted-shielded pairs. Aside from that, another possibility is MIL-STD-1553, which is transformer coupled differential signals. The 1553 standard can be downloaded from:

http://131.82.253.19/quicksearch/

or

http://assist2.daps.dla.mil/quicksearch/

Other possibilities are probably IEEE-1394 Firewire or AMD/Cypress Hotlink or even plain-vanilla Ethernet.

The basic concept is that you design the driver and receiver to operate by having the final signal be the difference of signals on two closely-coupled lines. Since they should have the same amount of noice imposed by the environment, the differencing should cancel out the coupled noise, leaving only internally generated noise.

TTFN