[sdiy] Voltage references in VCO

[René Schmitz]

Hi Benjamín and all,

Benjamín Velasco wrote:
> 1) the voltage divider at the neg input of Ub2 (comparator)
> 2) the 1 Meg resistor connected to +12 and the emitter of one of the
> transistors of the expo pair
> 3) the freq pots

Usually thats all in a VCO that is critical. (There are many more points 
where dirt on the supply can creep in. So keeping your supply clean is a 
good idea anyway. )

While you're at it also take the various offsets for the waveshapers 
into consideration. If you do that you don't have to worry about 
recalibration when your supply voltage changes.

> Will a 10V ref from analog do the job? (perhaps changing some resistor
> values). For example the AD587 or REF01

Sure. Its usually some easy applications of Ohms law.

You might need to change divider ratios to get the same voltage as 
before. Say a 5V trip point divided out of 15V requires a divide by 
three divider, but for 10V you only divide by 2.

Or take the reference current for the expo, 12V/1Meg = 1.2uA or 10V/820k 
= 1.21uA. (I wouldn't really bother with that anyway, since all thats 
going to happen is that you need to retune a little to compensate for 
that. There is a trimmer for the tuning anyway.)

Cheers,
  René

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