LT1997-2 Distortion Specs

Unlike traditional INA, an over-the-top (OTT) opamp has a transition region where the input stage goes between a common-emitter pair and a common-base pair as the common-mode approaches the upper supply. Since the offset is different between the two (usually much worse in the OTT mode) there is a region of significant non-linearity. Any signals that cross the transitional common-mode will undergo instances of distortion that would be difficult to characterize in a useful way, though I suppose a plot of the pure OTT mode distortion might have been of some value. We don't usually expect OTT mode to be the dominant operating condition for precision applications, but rather a means of avoiding hard clips or phase reversal under overdrive conditions (like servos for example). If your application is distortion sensitive and would tend to cross an OTT transition, then a different solution may be better. One alternative would be HV opamps (like LTC6090) along with LT5400 resistor networks.

In my application LT1997-2 internal OPAMP will operate inside [V– ; V+ – 1.75V] so it won't transition into OTT mode. The LT5400 solution will provide worse CMRR inside 0-1kHz range. I don't have oppurtiny to do the THD benchmarking on LT1997-2 eval, so I'm searching for any useful information here.