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

[HOSHUYAMA]

Hi Karl,

In the last weekend, I looked for the schematics I draw,
but unfortunately, I couldn't find them.  I'm so sorry.

In the schematic, I just inserted a 2164 as an summing amplifier 
in the CV path to the CV of another 2164 that is used as an 
exponential converter.  In another schematic, I inserted a 2164 in
the feedback loop of the CV summing opamp.
In both cases, the difficulties were the CV signal level, 
and trimming procedure.  We have to set the tempco coefficient, 
not only V/Oct factor.

As you imagine, what I was afraid is that the tempco 
coefficient has exponential function of the temperature.
I think we have to compromise about the coefficient 
as close as possible over some wide range of room temperature.

Best,

Sam HOSHUYAMA
Saitama, JAPAN

Date: 2007/04/04 23:07:32
karl dalen <dalenkarl at yahoo.se> wrote:
> 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
> > > 
> > > 
> > > 	
> > > 	
> > > 		
> > > _________________________________________________________
> > > Flyger tiden iv臠? F蚣ga dagen med Yahoo! Mails inbyggda
> > > kalender. Dessutom 250 MB gratis, virusscanning och antispam. F〓den p〓
> > http://se.mail.yahoo.com
> > > _______________________________________________
> > > Synth-diy mailing list
> > > Synth-diy at dropmix.xs4all.nl
> > > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > > 
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at dropmix.xs4all.nl
> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > 
> 
> 
> 
> 	
> 	
> 		
> _________________________________________________________
> Flyger tiden iv〓? F〓ga dagen med Yahoo! Mails inbyggda
> kalender. Dessutom 250 MB gratis, virusscanning och antispam. F〓den p〓 http://se.mail.yahoo.com
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>