An interesting paper about Vos Ios Ibias, how they come in the output offset of a FDA circuit using THS4551.
https://e2e.ti.com/blogs_/b/analogwire/ ... nt-and-why
This shows, on the given example:
Vos is the major contributor onto the output offset.
Next are Ibias and Ios which highly depend of resistors.
_Ios contibutes to output offset more then Ibias. Ios contribution depends of resistor values ( resistors 5 times larger give 5 times more Voos )
_Ibias contribution depends of resistor values and resistor tolerances.
Temperature drift: Same qualitative results.
It would be interesting to know similar results for a balanced circuit using two op amp instead of one as in the example.
It gives insights about the second stage of preamplifiers using two similar circuits to make a balanced output.
With similar Vos Ios and Ibias characteristics. The output offset voltage Voos+ - Voos- would follow the same qualitative results.
Vos major contributor
Ios contribution depending of resistor values
Ibias contribution depending of resistor values and resistor tolerances.
With other dissimilar Vos Ios and Ibias charateristics, the order in which they are important can be different and depend of resistor values.
I guess estimate that within the same op amp technology, results are the same.
I think the results are better thanks to some cancellation from op amp matching.
Who knows how Vos Ios Ibias match about op amps from the same manufacturing batch ?
Who knows when the op amps are in the same chip, as in a dual or quad ?
I think, going balanced gives better results, going balanced with a dual gives best, I guess estimate we gain 10 times better.
EDIT: I later found, my 10 times better statement is all wrong about the Voltage input offset. The LT1002 datasheet shows there is little gain from matching.
Needless to say, I will implement servo integrator circuits using duals like OPA2277 or ADA4522-2.
This paper gives me insights too, about how Vos Ibias Ios come in differential integrator circuits. Differential Deboo or else.
Thermal drift: When the two amps are in a dual chip, the two op amps are at near the same temperature, there should be about no residual drift.
A single op amp is subject to the ambient temperature. With two op amps in a balanced circuit the drift is subject to the temperature difference of the two chips, giving an order of magnitude lower drift. When in the same chip the temperature difference is very small, giving one more order of magnitude lower drift.