[sdiy] Voltage references in VCO

[René Schmitz]

Hi Rob and all,

Rob wrote:
> Hi

> Any additions/comments/corrections welcome!

No disagreement there, with careful notice of the big "IF". That is if 
the stuff that gets these stable references really good enough to really 
benefit from that. In a VCO that is peppered with TL084s the money for a 
<1ppm reference is just thrown out money. For that a Tl431, LM336 
(20-50ppm) is way better than the rest of the circuitry can handle.

Besides nobody is going to toss their old synths because they did use a 
LM7xxx style regulator... It was good enough for rock and roll back 
then, so why not anymore?

You might want to add a paragraph about choosing the right components to 
make the most out of these references. The performance should match.
It is very easy to spoil the performance. Opamp drift exceeding that of 
the reference for example.

Don't forget that you can't use metal film resistors anymore, since 
their 100ppm temperature coefficient even does exceed the precision of 
your reference. Even with the 25ppm types.

Cheers,
  René

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