[sdiy] Tempco adjuster idea

[René Schmitz]

Hi Ian, Magnus, Achim,

> Correct, but it is pretty close as long as you use a decent 
> transistor. Also, remember that Rene came up with a clever 
> improvement to the usual Rbe scheme that should take care of your 
> objections.

Remember the key (to most rBE compensations actually) is to have a
low reference current. Then it can be argued that when Iout >> Iref, 
where the flattening occurs, the difference between Iout+Iref and 
Iout-Iref is negligible.

However, I do not clearly see what rBE (which is genertating a
nonlinearity of the V/I transfer curve of the expo convertor) has to do
with temperature compensation?

> It could be the ultimate solution, although a bit inelegant.  One 
> thing to watch for would be whether the high temperature degrades any
>  component performance. You might want to get rid of all the 
> FET-input op amps, for example.

Has anyone ever examined how large the "open loop gain" of the typical
thermo servo is? I mean the gain would be expressed in °C/°C, then one
can apply the servo theory to see how good the regulation actually can be.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159