There are some JFET-input op-amps that have been released since Doug wrote his book that are worth considering:
The LME49880 is a dual op-amp with the usual JFET-input traits of negligible bias currents and low current noise. Voltage noise isn't too shabby at 7 nv/sqrt(Hz). The only drawback is a relatively high input offset voltage of ±5 mV (typ), ±10 mV (max). As one would expect for an LME49xxx part, it has exceptionally low distortion (0.00003 % into 600 ohms; yes, that's four zeros!) and isn't too expensive.
The ADA4627-1 (unity-gain stable) and ADA4637-1 (decompensated), as the part numbers suggest, are decent alternatives to the OPA627/637 with very similar performance but at half the price (still very expensive!).
Blog Doing Math in FPGAs Tom Burke 24 comments For a recent project, I explored doing "real" (that is, non-integer) math on a Spartan 3 FPGA. FPGAs, by their nature, do integer math. That is, there's no floating-point ...