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Wide ground trace

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dr.power

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HI guys,

In several PCB's I have seen the ground (plus some times the VCC and VEE) traces are much wider than the other traces. I know that the reason Is the CURRENT that the ground and may the VCC & VEE msut delivier to the differrent portions of the circuit. S the more current the wider trace is needed. But plz let me know if the Ground and VCC/VEE traces can help to avoid noise and so on when selected to be wider?
Actually I have designed a PCB for a Mike amplifier based on OP-amps, the ground/VCC/VEE traces are wide enough in my PCB, but I have afreedom to make the said PCB traces more wide. So plz let me know if it can do any improvement in NOISE and so on by wideing the said traces? I even can constracut a ground loop/guard on the surrounds of the PCB if needed.

Thanks a bunch.
 
Providing grounded copper areas around traces carrying signals is a common way of screening the signal traces from noise pick-up.
 
There is very little current in most signals. VCC and GND has much more current. Current in IC1 may cause the GND and VCC of IC2 to move. The resistance of the GND trace and current flow will cause the ground to change voltage. Beyond that traces have inductance. At high speed, traces can have large voltage drops due to inductance and high frequency current. You mentioned 'noise' as a reason for wide GND traces, it is more of a problem of cross talk, noise from one IC getting into the signals of another IC.

In multi-layer boards it is common to have one or two layers 100% ground. That way the grounds are all tied together very well. It is also common to have power layers that are mostly VCC.
 
Is what I talked about in my first post here is refereing as "Polygons" or something so?

Actually I myself guess that by using WIDE enough ground/VCC/VEE traces I end up with something like shields (Like what the shield cables do), right?
 
Yes, to a degree. Look up microstrip. Then look up stripline too.

Having a wide ground trace beneath selected signals is an effective way of reducing both crosstalk to adjacent signals and RFI.

Consider high frequency switching in a power supply or motor control. Assume you're rectifying AC and switching the high side to boost or buck the voltage to a different potential. Laying a wide ground trace all the way from the rectifier negative to the output ground and keeping the slightly narrower rectifier positive trace and the relatively high power switched output trace routed directly above this wide ground trace is effective at keeping switching noise from being emitted and showing up elsewhere in the circuit being supplied as well as maintaining compliance with FCC regulations.

At least that's been my experience.
 
Is there anybody to explain me what is a "FootPrint" in PCB field plz?

Thanks

Its the component outline, the area which the component covers over the PCB face....
 
Its the component outline, the area which the component covers over the PCB face....

Sorry Eric, But can yuo show me it by a pic plz?

By the way does the "Via" have any meaning in single liyer PCBs or it is just for multilayers?

P.S.Thank you very much for your PM too, Actually The POT name is a word that I learnt it via this forum.
 
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Sorry Eric, But can yuo show me it by a pic plz?

P.S.Thank you very much for your PM too, Actually The POT name is a word that I learnt it via this forum.
hi
This is a PCB laid out by 'Boncuk' I have marked the outline/footprint of the Relay in Yellow.

Thats the board space the relay occupies.
 

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the other imprtant question is, if there any rule saying the preference of 2 components connected to one trace? I do not know if it is clear or not, but for instance in an inverting op-amp one pin of the Rf is connected to one pin of Ri, so do I have a freedom to connect either the Ri's pin first to the "- op-amp" or the Rf's pin first when desining the PCB? or what about the other pin of Rf and the load's pin?
Make sense
 
hi
This is a PCB laid out by 'Boncuk' I have marked the outline/footprint of the Relay in Yellow.

Thats the board space the relay occupies.

Thanks a lot Eric,
It makes sense. So the footprint or so called PCB package in proteus software is the pattern or the demantions of it where I see in the pcb window. Actually the components in the PCB window called footprints, righ? But if we call it as the area occupied by the pins of the pcb components then plz let me know if it is just the pins or the complete area under the case?

Can you plz kindly let me know what is the "layout" too?

Thanks again
 
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Another question is that I do not know how does incarsing of the tracse width or lengh or even both affect the inductance of the traces? Any idea plz? I would like to see whether the inductance does incarse or it decreases as the resistance of the trace goes high? Any formula to show the realationship between the inductance and the Reistance of a trace plz?
 
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Did you down load from that link I posted in post #10, that covers most of the points you are asking.??

Hi Eric,

Yes I read the said paper and finished in 2 days. It did not cover NON of my 3 above questions, But anyway it was a good paper to make me familiar with PCB tips, Thanks for recommending it.
 
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