[sdiy] VCO tempco R locataion

[Stewart Pye]

I'm looking at Electronotes ENS76 type circuits so it would be going to 
the base of the transistor that carries the reference current.

Thanks,
Stewart.

JH. wrote:
> 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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>
>