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  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.