> very stable current source to drive transistor sensor

I was half hoping that the math that promises one-point calibration when
using the two-current method would also help if the current would change a
little bit together for the h and l value (it does not help). This was the
point of setting up the experiment as I did.

It is already known from at least two references that the system works
when done properly (and with lots of parts).

Peter

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