[sdiy] New Thomas Henry VCO-1 Page Up

[Neil Johnson]

Hi,

Ian Fritz wrote:
> In 2000 I made additional improvements, including using good modern  
> opamps (OPA27 for the CV summer, OPA134 for the CV servo and the  
> Schmitt trigger).  At the same time I added added temperature  
> compensation for linear temperature drift and tweaked up the scale  
> factor drift.
>
> My version of this VCO is now reasonably stable, although the use  
> of the supply rails for critical voltages is something I would  
> avoid in a new design.

It is a continual source of amazement to me that so much effort and  
expense is put into the choice of fast comparators, low-offset  
opamps, esoteric temperature compensation schemes, etc, only for the  
design to then rely on the supply rails for reference or other  
critical voltages.  Especially given the low cost and ease of use of  
even half-decent bandgap reference diodes available these days.

Neil
--
http://www.njohnson.co.uk