[sdiy] 2164 Expo correction

[David G. Dixon]

> From your two 
> datapoints the base current should change by ~0.2µA (that's 
> for two transistors) over the range you measured, which is at 
> least a plausible number (depending on what your input 
> current is, of course).  I've not done any further checks...

Does that mean that the relative error might be decreased by increasing the
quiescent current through the transistors (i.e., by feeding a significant
current into the MODE pin)?  I'm going to try that.  It's a long shot, but
what the hell...