SV: Re: [sdiy] SSM2164 and *one unit* tempco idea!

[karl dalen]

Sam!

I remember Roman was talking about temp compensation
when he did his SSM2164 VCO but didnt go futher since
he was pleased with the performance anyway.

I have been dealing with this idea for years but never
gotten my thumbs out to actually do something, but now
i think i at least have a try at it!

Do you have a schematic then i could compare my idea
with your to se what differs then report back to you
if i find anything that differs?

I think in your non tempco compensation idea you got 
a multiplikation factor thats not constant and you 
recognized it as non linearity as you did,it would
come from both internal expo trannies you are using
in your VCO.

Reg
KD



--- HOSHUYAMA <houshu at muj.biglobe.ne.jp> skrev:

> Hello KD,
> 
> I considered similar idea a couple of years ago, but abandoned. 
> (I'was and am thinking of 2164-based synth like Roman Sowa ;-)  
> Your approach looks different from mine.  I'd like to know the 
> details of your idea.
> 
> I tried to design a VCO (without tempco) using one unit in 2164 for 
> exponential converter and another for tempco.  The disign was very 
> difficult for me because its temperature dependency is not linear.  
> After compromise, I managed to draw a schematic.  However, I couldn't 
> think it is a better design than ordinary tempco-based method, 
> because it is complicated and requires adjustment.
> 
> Sam HOSHUYAMA
> Saitama, JAPAN
> 
> 
> Date: 2007/04/04 06:10:39
> karl dalen <dalenkarl at yahoo.se> wrote:
> > Idea!
> > 
> > In order to compensate for the temp drift in the SSM2164 one usually takes
> > a tempco, or ntc for each expo,but since here all the expos are on the same
> > die and therefore (not matched) but at least on the same die close they
> > would be quite equal in terms of temp drift one could take one tempco/ntc
> > thermally place it in contact with the top SSM2164 or below (missionary sex
> > formation) then take the sensed value, scale it to match each expo input
> and
> > then simply add this drift coefficient to each expo input.
> > 
> > The idea are instead of having four tempcos (which would be expensive)
> > you can use one dirt cheap NTC for instance, if the NTC bails the entire 
> > chip will bail instead of having to figure out which OTA of four or more
> bails
> > out in the case of using four NTC's.Also you save components, and PCB
> > real estate and its cheaper!
> > 
> > Ideas about this idea!
> > 
> > Reg
> > KD
> > 
> > 
> > 	
> > 	
> > 		
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