[sdiy] VCO tempco R locataion

[JH.]

Passive resistor divider means it must go to the base of the transitor that 
carries the *reference* current (not the variable current), or it will cause 
errors.
In feedback loop of opamp means no such error (low impedance), but it also 
means the opamp's input noise appears at the transitor base without 
attenuation, which may or may not be a good thing, according to your desigh 
philosophy.

JH.


----- Original Message ----- 
From: "Stewart Pye" <stewpye at optusnet.com.au>
To: "Synth DIY" <synth-diy at dropmix.xs4all.nl>
Sent: Friday, July 30, 2010 9:11 PM
Subject: [sdiy] VCO tempco R locataion


> I've seen that sometimes the tempco resistor is located in the feedback 
> loop of the CV summing op amp, and sometimes as part of a voltage divider 
> after the CV summing op amp. Is there a great difference in doing it 
> either way? I have read that there are inaccuracies when it is used in the 
> voltage divider...
>
> The reason I ask is that I have 1k tempcos so they would be more suitable 
> to use in the voltage divider.
>
> Regards,
> Stewart.
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