Thanks,
Ill post you a schematic if i may.
Its a led light.
We have a dimming pin (ADIM) into which we must feed a voltage >2V.....however, we put an RC delay of 10meg/10uF before it (for long softstart), and the unfortunate current out of the ADIM pin drops an unfortunate voltage across the 10meg resistor...therefore we buffer the RC on its way to the ADIM pin..............we have a 5V rail and since 5v>2v, we can feed that to the ADIM pin.......but as discussed, we must buffer it on the way to the ADIM pin......the opamp's input is the 5v.
We could divide the 5v down and then feed it to the buffer, but we are extremely space constrained, and struggle to fit in even two 0402 divider resistors.
Thanks Klaus you kindly explain the saturation situation...i am not sure if that matters for us, ...as long as the opamp output goes above 2V and stays there then we're ok.
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...ummm, ive just realised that what ive said doesnt "quite" make great sense.
....What i didnt say was that we actually have fitted the divider (into the opamp noninv input) just in case we wish to feed a dimming voltage <2v to the ADIM pin....(we fitted it but top resistor is zero ohms and bottom is not fitted.
...it gives us the option to dim it in future.
....when dimmed below 2v then the drop across the 10meg does matter.