a question about ip3 simulation using spectraRF

hi, when i simulate ip3 of an amplifier using spectraRF, the ip3 curve is not a straight line,but the the first order gain curve is straight. I don't know where i'm wrong.Who can help me ? Thank you

I am too
i have drawn nonlinear lines of iip3 but i cannot draw linear line of iip3
please help me

The straight line which you have seen in the textbooks is a theoritical/computed nonlinear behaviour..
So, the series expansion of current/gm/ etc.. is linear and time invariant...The coeffficients are always constant/real etc...
But in practice , coefficients are variable depending on OP of the device...
That's why any degree of nonlinearity can be slightly different...

See The Designer's Guide Community Forum - Class B RF Power Amplifier ,IIP3/OIP3 Spectre