[ sorry, reposting, forgot the tag.. ]

Hello EEs,

I would like to protect the inputs of a MCP602 opamp. My circuit is
ultra-high impedance, and has to remain the same in this regard. What
I did is adding a 10K resistor in serie, since the opamp will digest
up to +-2 mA, and I don't expect to find more than 20V on the inputs
anyway (20V/10Kohm=2mA).
Just for some added protection, I was thinking to add two schottky
diodes between the opamp input (thus after the 10K resistor) and the
power supply rails.

My concern is, will the linearity of my circuit be affected by the
diodes? Consider that some sources (whose voltage I have to measure)
will be truly high impedance, so that there may not be much current
to drive the opamp input pin (apart from the 10K resistor losses),
will the schottky diodes "signal" their presence someway when they
don't conduct? AFAIK they can have losses in the order of many nA,
this will apply because it's reverse biased losses, right? And if so,
what kind of diodes have a voltage drop low enough to be usable as
protection devices and have no reverse biased losses?

Thanks,
TPM 

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