Hi guys I have a problem regarding IIP3 plots. My IIP3 is not rising by 3dB. As I am designing a passive like attenuator and dealing with very low voltages, PSS and PAC simulators does not function properly when transistor Vds is close to zero. I have done the transient, reduced power and pretty confident that the circuit is working fine. But I really need to find a trust worthy way to generate the IIP3 curves as PSS and PAC analysis cannot be trusted. Now I am trying to apply a small bias voltage at the drain just to get the curves but that is getting things very complicated. So did anyone faced a similar problem and do you know way to get the linearity curves. Best regards
to get curves for linearity, I advise you to use the software "Agilent ADS2009" or 2011. here you can generate several types of IIP3 simulators.
good luck
Hey, we actually figured out the problem. Since you are interested this is what happened. It wasn't the issue with PSS and PAC analysis it is the BSIM3 transistor models do not function properly at vds near to zero hence gives a false IIP3 value. That is why it creates problem when you working with circuits which work as passive blocks. The work around we figured is to bias the transistors i a way that the vds is slightly higher than the value where the IIP3 increases with 3:1 ratio which it should. And extrapolate the values. It's quite a complex work around but we do not have BSIM6 or PSP models in our disposal. We are still trying to verify the workaround. We need the IIP3 curves to prove that our design is actually improving the linearity.
Best regards
Shashwata
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