As acknowledged by TI's John (who may now be retired), the OPA1641 has significantly reduced the common mode voltage dependence of the input capacitance from the initial product due to post-release process changes.
The modified f = 1kHz, Vin = 5Vrms, Rs = 10kΩ, THD (not +N) is now less than -120dBc.
Other relatively new TI JFET inputs, OPA827, 828, 140, 141 and 145, are all below -120dBc, outperforming most BJT inputs.
By the way, I don't like the way you say ‘just in the same way unusuable as most jfet op-amps for common mode’ without giving the required specification. There are plenty of places where a traditional JFET input OP-AMP would be sufficient.
You should say, ‘I am aiming for this level of performance in these applications, so I can't use it’.
The modified f = 1kHz, Vin = 5Vrms, Rs = 10kΩ, THD (not +N) is now less than -120dBc.
Other relatively new TI JFET inputs, OPA827, 828, 140, 141 and 145, are all below -120dBc, outperforming most BJT inputs.
By the way, I don't like the way you say ‘just in the same way unusuable as most jfet op-amps for common mode’ without giving the required specification. There are plenty of places where a traditional JFET input OP-AMP would be sufficient.
You should say, ‘I am aiming for this level of performance in these applications, so I can't use it’.