[sdiy] Question about my high freq compensation

[René Schmitz]

Hi Grant and all,

Grant Richter wrote:

> Would you would be kind enough to explain the improvement over the Rossum
> implementation?
> 
> I'm sure there is a reason for the increased parts count.

The parts count actually is the same, one trimmer, one resistor and one 
diode.

The key idea is that the end of the trimmer is connected to GND. (It 
would be left open in the Rossum scheme.) The diode now sees a current 
that is equal in magnitude to the expo current. Thus the Vbe drop across 
the right transistor is more accurately mimiced by the diode.
In the Rossum scheme only a tiny current flows through the diode 
creating much less drop than it would be desired.

Hope that clears it up.

Cheers,
  René

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