Diffstbprobe

Dale,

diffstbprobe is a newer way of measuring differential and common-mode stability when using spectre's stb analysis. It supersedes the old cmdmprobe component. It has the advantage of handling unbalanced loops - the old cmdmprobe didn't work properly if there was significant CM to DM or DM to CM leakage, but that's not an issue with the new component. Also, one additional benefit is that you can choose on the stb analysis form whether you are measuring common-mode or differential-mode stability, rather than having to alter a parameter on the instance of the measurement device itself.

To answer your specific questions:

1. I don't really understand the relevance of the link you gave - that's a general paper on testbenches for differential circuits, and doesn't mention measurement of stability using stb analysis
2. You point at the new probe in the same way from the stb choose analysis form in ADE.
3. I don't see why you should not be able to use stb analysis as an acnames/actimes option for tran analysis. I've done this myself several times in the past - if it doesn't work, check with customer support - maybe it was broken in a specific version (although I'm not aware of this).
4. Yes. You probably need to ensure you're running a recent enough MMSIM version though (all should be OK with MMSIM10.1).

Best Regards,

Andrew.

Dear Sir,

I am new in to the analog design, I started recently with the simulation of the fully differential amplifier. I used the Iprobe with the stability analyses and this method is working with me perfectly, however I am not of how to use it with the stability simulation of both the common mode and differential stability 

I would like to kindly show you the setup I am going to use and please confirm me if it is wrong or if there is other better setup than I showed

Thank you in advance

Dear Sir,

I am new in to the analog design, I started recently with the simulation of the fully differential amplifier. I used the Iprobe with the stability analyses and this method is working with me perfectly, however I am not of how to use it with the stability simulation of both the common mode and differential stability 

I would like to kindly show you the setup I am going to use and please confirm me if it is wrong or if there is other better setup than I showed

Thank you in advance

Those pictures are too small to see what you you're trying to illustrate.

Your setups for the differential-mode stability test both look correct. Your setups for the common-mode stability test (incorrectly labeled "Differential mode test") also look correct. However, a simpler way would be to use the same setup as for the differential-mode stability test (with the diffstbprobe placed directly at the output of the amplifier, before the common-mode tap) and just select "Mode Type: common" (instead of "differential") in the stb setup form (see below).

Thanks Frank. Your eyesight is better than mine!

Andrew.

Sorry Sir I am new to the forum, hope I will improve my post next time

Hi Frank,

I think the diffstbprobe is the iprobe connected between two ideal_balun.

As I remember, I have come across this from your post in some other place long time back.

Could you please tell how exactly the connections are with the ideal_balun that works exactly same as that of diffstbprobe.

Kind Regards,

Why do you need to know the internal details? diffstbprobe is effectively two baluns which convert the differential signal into the common-mode and differential-mode part, have an iprobe in each path, and then convert them back to differential again. The simulator then knows which of the two iprobes to pick based on which mode you've asked to measure stability.

Andrew

As far as I can tell, the diffstbprobe internally looks similar to this:

Thanks Andrew.

Sometimes we may need to verify the stability results by using simple AC analysis. Then using it appropriately for the current + Voltage source (which is the iprobe) as discussed in the Ken et al's Stability Analysis paper. 

Moreover, if we need to compare the circuit analysis results against the simulation results, there is a need to know how the iprobes are connected.

Kind Regards,

Thanks a lot Frank.