[SOLVED] How to extract parasitic capacitance of MOSFET

[ktx2222]

Hi everyone,

Can you tell me what method I have to use to extract parasitic of a MOSFET. I used S-parameter simulation:



I would like to know Cgs (gate-source capacitance). In the schematic, MOSFET was biased as operating point and I used very large ideal inductor to isolate effect of Cgd (gate-drain capacitance). So, Cgs=imag(Y11)/(2*pi*freq)=0.178 pF.

Please help me. I really appreciate your comments. Thank.

 

[BigBoss]

Extraction of intrinsic and extrinsic components is not easy from s-parameters.
For that target, modelling softwares are more useful but they are not available in a reasonable prices.Measurement equipments are also very expensive.
Instead, you may see modelled components by making a simple DC simulation at that operating point since the appropriate model is well known.Cadence ADE gives you almost these components and ADS gives you some important intrinsic parameters in Simulation-->Detailed Operating Point option but not all of them.

 

[ktx2222]

Extraction of intrinsic and extrinsic components is not easy from s-parameters.
For that target, modelling softwares are more useful but they are not available in a reasonable prices.Measurement equipments are also very expensive.
Instead, you may see modelled components by making a simple DC simulation at that operating point since the appropriate model is well known.Cadence ADE gives you almost these components and ADS gives you some important intrinsic parameters in Simulation-->Detailed Operating Point option but not all of them.

Thank BigBoss,

I run DC simulation and here is result:


Base on Agilent definition: **broken link removed**

=> Cgs (DqgDvsb) = -0.0562 pF and Cgd (DqgDvdb) = -0.0117 pF!!

What is the problem?

 

[BigBoss]

I have done a DC simulation with ATF series FET of Avago and I have found something more consistent rather than yours.So it may be variable depending on which foundry/model you use and ADS can sometimes extract more detailed sometimes not.I don't know why but there should be a reason..
As you may see, ADS has given me some important intrinsic parameters ( not all ) but it may not give them for all models/foundry models.( IP issues ???)
But I'm sure Cadence will give you almost all if you are able to download your foundry DK for Cadence.Otherwise I don't know any third kind solution.

 

[ktx2222]

Thank BigBoss,
I also used Cadence. I chose DC analysis (Save DC Operating Point). After simulation: Result -> Annotate -> Show parasitic and I got error:

Error* hdbGetLibName: argument #1 should be a hierarchical database configuration object (type template = "h") - nil
<<< Stack Trace >>>
(... in _mspsConfigToSchExt ...)
(... in _mspsInitConfData ...)
(... in _mspsGetConfData ...)
(... in _mspsGetSessionParCV ...)
(... in _mspsBackAnnotate ...)
(... in _mspsBAPushHilight ...)
_mspsBAPushHilight(path schCV ses)
when((_mspsIsSchInWindow(window(ses)) && (_mspsFlowIsEnabled ses ?flow flow)) (path = strcat(geGetInstHier(&) "/")) if(index(path "//") then (path = "/")) (schCV = geGetWindowCellView(window(ses))) _mspsBAPushHilight(path schCV ses))
foreach(ses (sessionContext->sessions) when((_mspsIsSchInWindow(&) && (_mspsFlowIsEnabled ses ?flow flow)) (path = strcat(& "/")) if(index(path "//") then (path = "/")) (schCV = geGetWindowCellView(&)) _mspsBAPushHilight(path schCV ses)))
progn((sessionContext = _mspsGetSessionContext(sessionId)) foreach(ses (sessionContext->sessions) when((& && &) (path = &) if(& then &) (schCV = &) _mspsBAPushHilight(path schCV ses))))
(val = progn((sessionContext = _mspsGetSessionContext(sessionId)) foreach(ses (sessionContext->sessions) when(& & & & &))))
let((val prevFlow) (prevFlow = _mspsGetFlow(sessionId)) _mspsSetFlow(sessionId flow) (val = progn((sessionContext = &) foreach(ses & &))) _mspsSetFlow(sessionId prevFlow) ... )
_mspsWithFlow(sessionId flow (sessionContext = _mspsGetSessionContext(sessionId)) foreach(ses (sessionContext->sessions) when((& && &) (path = &) if(& then &) (schCV = &) _mspsBAPushHilight(path schCV ses))))

I don't know what is this. I am newbie in Cadence

 

[BigBoss]

Make a DC analysis and Save DC Operating Point and then simulate it.
After Simulation, go to Results tab and select Annotate-->Model Parameters and then click the component on which you're interested in

 

[ktx2222]

Make a DC analysis and Save DC Operating Point and then simulate it.
After Simulation, go to Results tab and select Annotate-->Model Parameters and then click the component on which you're interested in

BigBoss,
I did as you told and I just saw:

BTW, can you tell me what is "vsat"

 

[wiir2000]

voltage at saturation mode, i guess

 

[ktx2222]

voltage at saturation mode, i guess

Thank wiir2000, vsat=189K. I don't think it means 189000 V(!?)

 

[BigBoss]

BigBoss,
I did as you told and I just saw:
View attachment 111202
BTW, can you tell me what is "vsat"

Try also Print-->Model Parameters

 

[ktx2222]

I have done a DC simulation with ATF series FET of Avago and I have found something more consistent rather than yours.
As you may see, ADS has given me some important intrinsic parameters ( not all ) but it may not give them for all models/foundry models.( IP issues ???)
View attachment 111181

Can you give me your ADS setup simulation as zap file. In fact, I don't know what is "ATF". I really need it. Thank you so much!