0 Members and 1 Guest are viewing this topic.
Some circuits require constant ratios among a number of resistors but not the absolute stabilityof each individual resistor. For example, the accuracy of an operational amplifier depends onthe accuracy and stability of the ratios of the input, feedback, and bias resistors; if all resistorsmove together to maintain the constant ratio, the op amp accuracy remains constant. Theresistor manufacturer may test resistors and select a set with a good TCR match to achieve the Facts a GlanceFrom: Vishay Foil ResistorsJuly, 2013FACTS #121- 4 -required ratio stability over a defined temperature range. But this neglects the power-induceddivergence of resistance values through service life.
I would say it is how many ohms a resistor changes for every degree of change
Absolute is opposite of Relative.QuoteSome circuits require constant ratios among a number of resistors but not the absolute stabilityof each individual resistor. For example, the accuracy of an operational amplifier depends onthe accuracy and stability of the ratios of the input, feedback, and bias resistors; if all resistorsmove together to maintain the constant ratio, the op amp accuracy remains constant. Theresistor manufacturer may test resistors and select a set with a good TCR match to achieve the Facts a GlanceFrom: Vishay Foil ResistorsJuly, 2013FACTS #121- 4 -required ratio stability over a defined temperature range. But this neglects the power-induceddivergence of resistance values through service life. http://www.vishaypg.com/docs/63517/FACTS-121.pdfSo absolute is as it says the absolute drift of a resistor, not the relative drift between resistors of the same type (which might be lower if you expect resistors of the same composition to have similar drifts). At least that's how I am parsing it.
Quote from: pitagoras on June 05, 2017, 04:27:24 pmI would say it is how many ohms a resistor changes for every degree of changeIt would still be the same if we omit the word absolute refer to any opamp datasheet and look at Vos drift, there is no absolute there!
It would help if you show us the context. Absolute might indicate that it is expressed in ohms rather than ppm (i.e. relative to the resistor value).
8ppm/°C Absolute Resistor Value Temperature Drift
Quote from: pitagoras on June 05, 2017, 07:11:43 pmIt would help if you show us the context. Absolute might indicate that it is expressed in ohms rather than ppm (i.e. relative to the resistor value).from LT5400 Datasheet:Quote8ppm/°C Absolute Resistor Value Temperature DriftLT5400It is indicated in ppm not in ohms!Which lead me to ask, which is important? the relative or the absolute drift?
LT5400 is a quad matched resistor network, so that's why they feel the need to call it absolute to let you know that they mean absolute not compared to the other resistors in the network. There is no need to call something absolute when talking only about one resistor (as opposed to a matched resistor network).
Quote from: Muxr on June 05, 2017, 08:43:15 pmLT5400 is a quad matched resistor network, so that's why they feel the need to call it absolute to let you know that they mean absolute not compared to the other resistors in the network. There is no need to call something absolute when talking only about one resistor (as opposed to a matched resistor network).In Vishay datasheet VHP100 They have mentioned thisAbsolute resistance change (window): VHP100 < 60 ppm (- 55 °C to + 125 °C)VHP101 < 10 ppm (+ 15 °C to + 45 °C)What is the meaning of "absolute" in this datasheet? There is no mention for a resistors array(which is obvious!) to have a need to say absolute! And what does window means?They have mentioned also it is zero TCR in the title !!!! Why if they later said 10 ppm