How to calculate the min. feedback resistor value in op-amps.

[Mark Tillotson]

Thanks for the help everyone! I think the thread answers many questions with feedback in an interesting way. I think it's time to experiment a little. Maybe I will design some matrixes of resistors for the experimentation. Maybe I can also measure some THD's for low frequencies?

Yes, do that, but if the resistor is reasonably rated for the dissipation and metal film / thin film its going to be a small effect only at lowest frequencies. Using a 0.1% metal film with 25ppm tempco will nail the issue as temperature variations matter way less for a very-low tempco resistor.

 

[Piotr]

Yes, do that, but if the resistor is reasonably rated for the dissipation and metal film / thin film its going to be a small effect only at lowest frequencies. Using a 0.1% metal film with 25ppm tempco will nail the issue as temperature variations matter way less for a very-low tempco resistor.

I have quite exspensive colection of X, Y, Z-foils ranging from 0.2 to 5PPM too. I'm not using them anymore anywhere. There is something wrong with them, with this foil construction. I think that normal 25PPM metal films are ok as you said.