Op amp gain calculator

[imhereithink]

Just wandering if anyone here has come accross this to work out their values of resistors to set the gain with an op amp

http://www-k.ext.ti.com/srvs/cgi-bin/webcgi.exe?Company={5761bcd8-11f5-4e08-84e0-8167176a4ed9},kb=analog,case=obj(32618),new

Im slightly confused with the terms, resistor sequence, and resistor scale? Any advice would be greatly apreciated.

Cheers

 

[Tomble]

Im slightly confused with the terms, resistor sequence, and resistor scale? Any advice would be greatly apreciated.

Cheers

Eh, the "resistor sequence" would refer to the um, set of resistors you'd be choosing from. EG: the set that goes "100, 220, 470, 1000" is the "E3" series; the "E6" series goes uh, "100, 1something, 220, 330, 470, 680(?), 1000". The E3s have 3 values before going up to the next power of 10, the E6s have 6 values before going up to the next power of 10. Someone else could probably say it more clearly than that You've presumably noticed already the pattern in the resistor (or capacitor even) values, anyhow.

"Resistor scale" I guess would be the order of magnitude you'd be aiming for, maybe for the total resistance, or for one resistor or the other, I dunno.

Personally, I'm not sure how useful this calculator is, seems like the most useful feature it'd have would be selecting specific values, whilst it might be nice if it could help you choose an appropriate scale of resistance for potential dividers in general, based on requirements. But maybe that's just me

 

[Hero999]

https://www.logwell.com/tech/components/resistor_values.html

 

[Tomble]

Hmm, that's peculiar. Should I take it that in that list there,
"E3 50% tolerance (no longer used)"
is referring to the "50% tolerance" being no longer used, rather than E3 series values*? Because I've got an E3 series resistor kit, but they're just ordinary 5% ones. And a good few circuits still seem to use either E3 or E6.

(*-yes I do get that those values would also be used in every other series)

 

[yngndrw]

The 50% tolerance does NOT mean the tolerance band of the resistor. It means that between available values (E.g. 100Ohms and 150Ohms) there's a gap of 50%. Therefore the closest available resistor could be upto 50% away from the required value.

Notice how in the E192 series, the values go up in 1's.

 

[Hero999]

What that chart also means by tolerance is that you can't buy resistors with a higher E rating than their tolerance. For example, you can't buy 5% tollerance resistors in E48 values or 2% tollerance resistors in E96 values.

yngndrw,
Note that the E192 series goes up in 1s at the start of the series and 12s at the end, it's a logarithmic scale - that's the whole point.