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Subject:	RE: [geda-help] General PCB Layout Question on Two Layer Board
Date:	Sun, 30 Aug 2015 21:13:53 +0300
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Keantoken wrote:
> You want all  
> significant currents to be in pairs so that the fields will cancel. It  
> helps to know which nodes in your circuit are susceptible to leakage  
> from which other nodes and which kind of parasitics. You can identify  
> several traces which hardly matter at all and abuse them to make room  
> for the important traces. And often you can also say that a parasitic  
> will be helpful at a certain node. 
>  
> Using a uniform ground plane with a 2-layer board means your traces may  
> have to be MUCH longer and thinner in order to get everything without  
> jumpers. So a good question to ask is, when do the parasitics of a long  
> and/or thin trace outweigh the benefits of a ground plane?

Keantoken is right. I've build small video amplifier with SMPS with only 
two rules: Think about return path and keep loops short. PSU gave 
3V 1A from 12V. I used separated ground planes for PSU and amplifier.
It isn't that big sin if you have trace same direction as return current but
across the current flow is bad.. 

The big trickery I did was adding piece single layer board over amplifier input
trace to cover it with signal ground. That cancelled almost all noise from input.

There are also some good graphs in Ott's EMI book. Select right way to
bring in the inputs and export outputs. Text is also good...

Anyway, try and prototype. Remember to have fun with electronics. That's how
you learn and some day you'll have revered grey beard.

--
Hannu Vuolasaho

 		 	   		  

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