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How to optimize large transistor layout for RF PA

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Newbie level 6
May 22, 2004
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rf layout

Hi all,

I'm drawing the layout for a rf power amplifier and I would like to know if there are other ways of optimizing the transistor (other than finger) to reduce the parasitics of the transistor?

What are the techniques used normally for drawing transistor layout in rf power amplifier?

Common Centeroid

Transistor Matching


The techniques that you refer to are mostly used for matching or is it used for wide transistor layout in PA?

some of the precautions to be taken while connecting power transistors are

see that metal width are eeting their specifications

keep metal slots in large width metal wires which are connected to pa

place as near as possible to pads

route these metala as short as possible with less no of tilts

if possible use commoncentroid or else even interdigitised method if it also nott possible just place all the fingers directly in a continuous line

but take care that they are near to the pads

i think this might be helpful or else plz eloborate ur quiry

Take advantage of the finger structure by interleaving forward and return current pathes. Some 100pH will impact at least your simulation result if not the performance or stability. Make a subcircuit modelling of the PA layout. IC RCX extractors are useless because the inductive coupling is not extracted. If 10mV is the error tolerance of the extraction and 200mA at 5GHz are flowing trough your layout the extraction should be accurate to 1.6pH(1.6e-12H)!!!. The extration tools today are focused on digital. So there is no market. But FastCap and FastHenry are useful or doing planar EM simulation.

Is interleaving the current path forward and return, a way to reduce the inductance of the PA?

Is there any references or papers to show how to model the inductance in the RF PA?

heat dissipation have to be considered for PA

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