[sdiy] Tempco adjuster idea

[Magnus Danielson]

From: René Schmitz <uzs159 at uni-bonn.de>
Subject: Re: [sdiy] Tempco adjuster idea
Date: Sun, 27 Apr 2003 18:06:38 +0200

> Hi Magnus, Ian,
> 
> > Which of them? I've lost track really...
> 
> There was only one. And it is an unpublished circuit, besides of that I 
> send them to you and Ian as attachement, back then.

Yes, we had a nice little off-list discussion.

> > My point was that there is two rBE to compensate, and they run under sufficiently
> > different conditions since the current through the two rBEs is not nearly the same.
> > On the reference transistor, the steady state current is almost perfectly the same
> > all the time. On the output transistor it varies over a huge range.
> 
> It was that I pointed out that its *only* the output resistors rBE that 
> is actually to be compensated. You accepted that argument.

Yes, but I recall (admittably this is vaugly in my memory) that I did contribute a
further refinement. Well, well.. the most important lesson is the fact that there is
two rBEs to compensate and they have different properties.

Sorry if I unintentionally tried to rob you of any credit of invention.

> The input transistors rBE results in a constant offset of the Vbe, which 
> translates into a fixed detuning. (Leaving possible higher order effects 
> aside.)

Right.

> > I had some proposals for how to remedy that as I recall it. I think it came out of
> > refinements of Rene's curcuit, but I don't recall it exactly now.
> 
> There is nothing to remedy, because there is nothing wrong with that fact.

Better dig back in time...

Anyway, Rene made a good point when he pointed out the halting rBE thinking in
previous work.

Cheers,
Magnus