I know how they do predistortion, was thinking to build ultra low thd generator ( <-120 dBc). Can't find an adc that could prove my algorithm is good. ADS127L01 comes in "hate to solder" package. And evaluation board costs a fortune.
Though, it would be quite expensive method to correct cheap OPA non-linearity by introducing extra linear adc on chip, converting input to digital, pre-distort, than convert back to analog again by extra linear dac, don't you think?
It would be expensive and also futile because there are simple techniques to reduce distortion in differential input feedback amplifiers. Once these are used to remove first (second?) order distortions, improvements through digital distortion correction would be futile because distortion can be below the noise floor.
These techniques are not often used simply because distortion is already usually better than needed and even less understood because they are easy to overlook in other designs. They include:
1. The most obvious one is to use inverting instead of non-inverting stages to remove common mode effects.
2. Match the impedance and not just the resistance at differential inputs.
3. Bootstrap the supplies to increase common mode rejection.
4. Unload the outputs of integrated devices to remove thermal feedback.