INA 128 characteristic - how to read it?

[glias]

INA 128 characteristic

Hi all, I would want to understand what this characteristic of op amp means ?

**broken link removed**

it is an extract of the datasheet of INA128 op amp...

regards

 

[karesz]

INA 128 characteristic

Hi,
these means only, that if your common mode Voltage at the Op input goes higher, you can take it(the Op) only with smaller signal/gain, because the usable output voltage range will be lower...
Remember pls: your signal is real superpositioned on Common Mode (Dc) voltage...
K.

 

[glias]

Hello and thanks for your reply
I'm not sure that I understand you... I will take an example :


if I have an instrumentation stage for measuring the voltage of a shunt, imagine that this shunt is connected to +28V and the other pin of this shunt is connected to antoher things... The supply of op amp is +/-15V, so if I respect the specification I can't do this ! because my op amp "see" a common mode voltage which is too higher than it can support is that right ?

And if I see the figure, I saw that the common mode voltage supported by the op amp is better with higher gain and is also better when the output is close to 0V.

thanks for your help
regards

 

[karesz]

Hi,
These was a seedy answer, for details, dependig on situation, you can be a part right (ca. 10% higher range with gain 10 to 1) on your diagramm, but for details refer pls to datasheet, especially pp.5..7.

The shunts other pin can not be connected "to another things", than their voltage drop is so smll, that the both pins are at similar, usual in 0.1--0.5V, potencilas.
Common mode input range is clear declared on page Nr2!
It must be under the +Usupply with 1.4..2v!, also must be less, & over the -Usupply!...In practicum: with +/-15V, Ucmmr = +13....-13V is real.
K.

Added after 3 minutes:

Dont confuse with input protection range, these can be over supplies( up to +/-40V specified), but as pp6 demonstrat, its working modus is no more linear, its simple PROTECTED_will be not wrong!!