I have downloaded the SPICE model file for the OP177 but found that it actually contains the model for the OP1177.

Where can I get the proper SPICE model file for the OP177 ?

Kai,

A spice model is a macromodel; the average op amp has 50-100 transistors. Most op amps are

junction-isolated, so every transistor is diffused into a silicon substrate, creating a parasitic,

reversed-biased diode to the substrate. In the old days of Intel 286s, if we gave you the actual

netlist and you used it for an 8-pole filter, it would take an hour or more to run a simulation. So the idea of

a very simplified model was born. Here is a good historical overview:

http://cds.linear.com/docs/en/application-note/an48.pdf

You are assuming that the macromodel exactly matches the actual silicon. Sometimes we get

close, but they are simplified. Some models don't model model voltage noise for example.

Some model flatband voltage noise, but not 1/f noise for example.

I would not trust any model from any manufacturer for what you want to do. Take the min/max numbers

from the spec table and use a spreadsheet.

-- Are you building the classic four resistor difference amp? If so, the resistors are more of a limiting

factor than the op amps.

-- Can you post a simplified schematic?

Harry