[sdiy] fast opamp with low offset

[David G. Dixon]

> Haven't followed too closely, so this perhaps isn't helpful, but
> nevertheless:
> If you want a current-input current-output RC lowpass, you have to
> put our well-known voltage-input voltage-output RC lowpass backwards:
> the resistor still goes from input to output, but the cap to ground
> is on the input side. Think of it as a current divider rather than a
> voltage divider. Part of the current (the higher frequencies) goes
> directly to ground via the cap, the other part of the current goes
> via the resistor into the (low input impedance) current sink.

Ingo, that's exactly what I've done!  I think of it this way: since I'm
filtering out the noise from downstream, the effective path of the signal is
upstream, and the filter must be pointed in that direction.  Should work
very well, as long as the resistor doesn't compromise the ability of the
2164 to generate its current.