Noise model of ADA4899-1 for LTspice

Document created by analog-archivist Employee on Feb 23, 2016
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When doing a noise analysis in Spice (LTSpice) using the model provided for the
ADA-4899, the noise output is orders of magnitude larger than specified in the
datasheet.

At first glance it seems like a noise current of ~12 nA/√Hz is flowing out of
the non-inverting pin (not the case for the inverting pin.)

Noise is a defining parameter in my design and the choice of component is
likely to be made based on the Spice, so I'd appreciate your opinion.

 

It is possible to change the model noise generator sources to accommodate for
LTspice but as suspected this is not something we have done. However I can tell
you how the noise can be changed if you want to try it:

.MODEL DEN  D(IS=1E-9 RS=1000 KF=1.5E-12 AF=.89)    (KF and AF are usually what
is causing the difference between Ltspice and other simulators)
.MODEL DIN  D(IS=.85E-9 RS=1 KF=1.5E-17 AF=.92)

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