thanks Jram, that's what I was wondering.
The ALD parts pretty interesting, I was not aware of them.
Looks like overall accuracy will be largely governed by gm mismatc in the mirrors. I would
be curious to know how your spice sims work out regarding this. However the PSOC IDAC
has a 5% error. But PSOC reference is good to .1%. You could either run a cal routine with
DelSig to alleviate this or use a Vref derived I source/sink, instead of IDAC. Decision governed
by doing an end to end error analysis to see if it meets your goals.
I assume you will be measuring the Vload having excited tissue with Iload. If you are using
PSOC that of course will violate CM range for pins / A/D, eg. complience needed at load.
Looks like isolated diff amp possibility, gets rid of ground CM as well. Analog Devices
comes to mind.
Very interesting design.