Hi, All ! Another option for low distortion OP amp is OPA134/2134/4134. The datasheet says it has -98 dB IMD3 and 8nV/root(Hz), note that is has FETs on input and provides that noise density at much higher source resistance than AD797. I use both of them in my DSP transceiver design and I am pleased with their performance. All the best ! Oleg Skydan 73 de UR3IQOLINRADDARNIL