the difference between OPA2192 and OPA2197?

Nimp,

e-trim is a trademark of TI. It is package level trim for minimizing offset. As you might know, there are couple different methods to trim offset, such as laser trimming, and chopping. Laser trimming is done at wafer level, which would be time consuming, and relatively high cost. E-trim, since is'ts done after packaging, there would be no offset shift due to the stresses introduced in the packaging process. In the case of package level trimming, the adjustment is done after the packaging, so this method is not affected by packaging stresses. Also, e-trim results in lower cost.

Here is the link to a blog on the e-trim topic.
e2e.ti.com/.../how-does-package-level-trim-compare-to-other-offset-correction-methods

-Ying