[SI-LIST] Re: parasitic elements of SMD resistors
- From: "eoin.mcgibney" <eoin.mcgibney@xxxxxxxxxx>
- To: jan.vercammen1@xxxxxxxx
- Date: Fri, 09 Jan 2009 11:44:56 +0000
Hi Jan,
If you have a VNA handy, you could always get a small FR4 test board
(using the material (maybe vendor as well?) you entend on using) made up
with footprints for the different size passives and measure their
s-parameters. You could fit the s-parameters to a equivalent RLC
circuit, i think thats how murata do it - if i remember they used to
have a library you could download which supplied s-parameters and
equivalent circuits for their range of passives.
Regards,
Eoin
steve weir wrote:
>Jan, if you want a really accurate answer then a 3D solver is your
>friend for this type of work. Pick any of the commercial tools and you
>ought to be able to get a reasonable result. If you are willing to put
>up with the UI, the free FFS programs FastCap and FastHenry should be
>able to get you close. Of late I have spent most of my time with Simbeor.
>
>Steve.
>jan.vercammen1@xxxxxxxx wrote:
>
>
>>Hello si-list,
>>
>>I am working on photo-multiplier tube electronics. I am interested
>>in the capacitive parasitic elements of surface mount resistors 100K-500K
>>(type
>>0805-0603) mounted on FR4 PCB - substrate height range about 0.5mm
>>above th GND plane. My interest is primarily on the parallel capacitance.
>>
>>I googled but came almost empty handed. I have information from
>>IEEExplore on photo-diode transimpedance ampli's where the parallel Cp
>>capacitance quoted is 0.1pF (R>1Gohm, Tyco HA type, SMD?, see paper
>>"How to enlarge the bandwidth without increasing the noise in
>>OP-AMP-based transimpedance amplifier", Ciofi et al.)
>>
>>Vishay reports on high-frequency SMD resistors (type CF20):
>>0.026pF for 0402 and 0.040pF for 0603
>>
>>Murata's impedance library gives the following data (on SMD inductors):
>>0.09pF for 0402 and 0.16pF for 0603
>>
>>I prefer the latter data because these likely reflect conditions we will
>>experience
>>on FR4 PCBs.
>>
>>Any suggestions for additional data on parallel and shunt capacitances of
>>SMD resitors mounted on FR4??
>>
>>
>>
>>Jan Vercammen
>>EMC/Signal Integrity Engineer
>>
>>
>>
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>
>
>
>
--
_______________________________
Eoin Mc Gibney
Test Development Eng.
Audio & Video Products
Analog Devices B.V.
Tel: +353-61-495918
Email: eoin.mcgibney@xxxxxxxxxx
_______________________________
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