What it the OIP3 of the LT5514 as a function of input drive?

Question

I'm considering the LT5514 because of the OIP3 value rated above +50dBm in my frequency range of interest. How can I determine the OIP3 as a function of drive level? Is there a model somewhere that I can use? I can't find any recent differential amplifiers in LTSpice. The reason I ask is because I see non-constant OIP3 in the datasheet plot of the AD8375 differential amplifier (Figure 11). I can understand why the (input) IIP3 might change as a function of gain in the VGA stage, but I can't understand why the OIP3 would change. I don't see OIP3 vs. drive level in other differential amplifiers and I'm concerned that there is a behavior in these high performance devices that is not able to be simulated in traditional system lineup. 
 I have also noticed this change in OIP3 in my measurements of the LTC6432 evaluation board. 
 I'm trying to design a high performance system that will use the LTC2208 ADC, but I'm unable to estimate the system linearity because of this unusual change in OIP3 as a function of drive level.

GLADION · Accepted Answer

Hi sanjosanjo , 
 
 Good day. 
 
 In an article by Kuo-Chang Chan entitled "The IP3 Specification", the OIPn can be directly related to the gain and IIPn of the device, that is, OIP(dBm) equals the sum of the gain in dBm and IIP(dBm). 
 
 In particular, OIP3 could also be measured as a function of the output signal and the change in the output signal as compared to the first-order frequency. 
 
 There were many other factors that could affect the OIP3 performance of a unit such as the frequency and resistor network used. You may want to check this out discussing a more detailed way of measuring OIP: www.analog.com/media/en/technical-documentation/tech-articles/ip3-and-intermodulation-guide--maxim-integrated.pdf . 
 
 Hope this helps. Thank you. 
 
 Regards, 
 Gilbeys)

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What it the OIP3 of the LT5514 as a function of input drive?