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[SOLVED] power amplifier line width

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sohaee

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Hi every one!
I want to layout a PA in CMOS, I know the maximum current density, allowed for the lines, my question is that, should I choose the line width for the DC current or the peak current?

If the answer is peak current, then should I be careful for high currents at the start of the operation? I mean the transient region. that will be too much then!

would you please help me?
 

Hey,

You should consider RMS current, which is the Ipeak*SQRT(Duty Cycle). The reason is that the RMS is what actually generates heat.
 
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    sohaee

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Hi,

True.

Just a remark:
Some (true) RMS measurement devices block DC for the measurement.
They show "0 A" when there is pure DC current. They show only the RMS of the AC components.
But here you need to take DC into account for the RMS measurement.

Klaus
 
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    sohaee

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The reason is that the RMS is what actually generates heat.[/QUOTE said:
Thank you so much for answering.
Is the heat the only consideration we must take? I mean, maybe for heat we should take care of RMS current, but what about Electromigration? I think that depends on DC current. Do you know if there is a rule or another maximum current density for that?

Thanks again!

- - - Updated - - -

Thank you so much!
Good point!I will take care of that.
Also, would you please take a look at what I asked Romansh, too?
Click to expand...
 

Thank you again for answering and the article! But still, I think, this is the DC current which leads to electromigration, As it is mentioned in the article:
" However, one must realize that Joule heating is caused by root mean square (RMS) current and not by the average current, as is electromigration."
Anyway I think what you said is true, and if we take care of RMS current, in the way KlausST mentioned, In fact, we have seen DC current, too.
Again I want to thank you both for your very kind help!:)
 

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