[sdiy] Active VCO temp compensation

[Jim Patchell]

As far as temperature compensation goes, there is no difference between 
the MAT04 and the CA3046.  There is a difference in tuning accuracy. 
With the MAT04, I can tune over 8 octaves with +/- 1 cent accuracy, and 
with the CA3046 I get +/- 1 cent over 7 octaves.

I haven't checked any of the oscillators lately, but they have also 
maintained their tuning very well over a long period of time.  What I 
like best about them is that I can build stable oscillators with low 
cost components.

-Jim

Luís Marka wrote:
> By the way, I see Jim has 2 versions of this VCO: one uses a MAT04 as 
> the matched transistor array, while the other uses a CA3046. Is there 
> any difference in performance between these? The CA3046 is much easier 
> to find (at least, where I live...)
> 
> Luis Marka
> 
> Simon Brouwer wrote:
>> Jim Patchell has some real nice documentation on his VCO that uses this
>> approach: http://www.oldcrows.net/~patchell/synthmodules/vco.html
>>
>>
>> George Hearn schreef:
>>  
>>> I'd like to modify my polysynth design to use active temperature
>>> compensation by making the VCO's output a temperature reference voltage
>>> that
>>> has a TC of 3300ppm/c.  This would then be used to derive the DAC
>>> reference
>>> voltage in order to compensate for the VCO exponential converter
>>> temperature
>>> drift.  I would like to do this by using a MAT04 quad matched pair or
>>> LM3046, using two transistors to make the exponential converter and
>>> somehow
>>> use the others to generate a voltage proportional to Vt.  Does anyone 
>>> have
>>> any ideas?  The CEM3374 had this arrangement and it was successfully
>>> employed in the Oberheim XPander and Matrix 12.  Regards, George
>>>
>>> _______________________________________________
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>>>
>>>
>>>     
>>
>>
>>   
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