Sat May 31 02:44:35 EDT 2014

Diode filter pinned between voltage and current source

Place ladder in between a voltage source and a current source. 
- DC voltage bias + AC input  at voltage source side, 
- DC current bias + AC output at current source side.

Making the dual of the one-pole filter at [1] it seems clear that the
signal needs to be injected at the V_cc side in my circuit.

The AC voltage source acts as transformer coupling.
How to do that then?

Wait.. The diode string can just be fed from a summing amplifier that
produces a DC offset near Vcc + the AC voltage.

In my circuit this needs a rail-to-rail opamp (e.g. MAX4167, MAX494,
MCP6244), or a lower DC voltage, say 2V.  Is there enough room to run
the diodes?  With just 3 diodes at a lower current that should work.

Or an emitter folower with an AC signal coupled in.

[1] http://www.experimentalistsanonymous.com/ve3wwg/doku.php?id=diode_ladders