EMC transistors design pcb

[tlz]

Hi,

I'm designing a PCB really simple with connectors, resistances and transistors. There are some rules that should be followed to pass the EMC test.
1. Using only 2 layer PCB is better to use ground planes in both sides.
2. Place decoupling capacitor between gnd and power in each active component. Place bypass capacitors if it's used high frequency.
3. Shielded the cables with bypass capacitors or filter pins.

My doubt is in relation with the transistors. I don't know if it's necessary attach to each transistor a decoupled capacitor between gnd and power, I'm not sure. Anyone knows about it?

 

[marce]

!
Why is a two layer design better than ground top and bottom, this is a bit of an ambiguous comment...
Decoupling and bypass are generally referring to the same thing....
Shielded cables with bypass caps , again a bit obscure...
Please elaborate and provide more info because I am at a loss here trying to understand your requirements..... And from my EMC experience your generalisations are vague to say the least and rather oversimplified considering I have at least two books for Electromagnetic Compatibility Engineering.

 

[tlz]

Hi,

I read that:
To use 2 layer instead of 4 layers, it's better to place ground planes in both layers to minimize the EMI problems. Is it not correct?
Decoupling capacitors should be attached to each active components and a larger bulk decoupling capacitor for each voltage distributed on they board.
Shielded I/O cable connectors equipped with bypass capacitors or filter pins.
My doubts are:
I'm going to use 2 polygons planes for ground in my PCB because I have two different voltages that are coming from outside and I need to separate the two parts of my circuit. I think that I need a bulk decoupling capacitor for each voltage that comes on to the board.
For the transistors I was thinking to use in each one a decoupling capacitor, between gnd and power, but I'm not sure about the value, how can I choose the value of the decoupling capacitors? I read that I can use 0.001 uF, 0.01 uF or 0.047uF.
I am also use an external power supply without wire to earth and attach this earth to one of the earths inside my pcb through a capacitor, what do you think?

Am I right to my conclusions to design according to pass the EMC test?
I would like to know some books about EMC too, could you pass me the name of them?

 

[marce]

Henry Ott
http://www.hottconsultants.com/


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