limitation of opamp's gain

[020170]

nowadays I read Some paper writtend by R.Poujois, deal with low drift fully differential opamp.

when I read the paper, I had one question.

in paper, the author say that " We must avoid saturation of the amplifier by the opamp gain product offset voltage at the output. So a limited Value of the voltage gain per elementary stage is allowd ( Av << 100 ) "

I don't understand what he mean.

why we have to limt gain of opamp to avoid saturation at output?

I don't know the meaning of "saturation at output"

thanks.

 

[thuvu]

Saturation is when the amp reaches the max value it can produce and it depends on supply voltage.

So if you have an opamp at +/-15V you can't get above 15V at output. If you have an amp of gain 100 and an input signal of 150mV the output must be 15V. If you try any larger input signal the output will still be 15V max.