VCO hacks, tweaks

[Rene Schmitz]

At 15:13 04.11.98 +0200, you wrote:
>I fear this issue is even more complicated if you opt for really
>accurate compensation.
>
>The problem is that the temp coefficient of the scale factor is a
>non-linear function of temperature. 3300ppm/K is accurate only around
>30 deg(C) (303K), since
>
>(303 + 0.5) / (303 - 0.5)  =  1.003306
>
>At 40 deg(C) (313K), which perhaps is closer to the operating temperature
>of an enlosed circuit, the required compensation coefficient is
>
>(313 + 0.5) / (313 - 0.5)  =  1.003200, i.e. 3200ppm/K
>
>In other words, using a (linear) tempco resistor isn't the most accurate
>compensation method, although it works well enough for most purposes.
>
>-joachim

I agree (since my spice simulations showed it), but I can't follow the
maths here
Ok 303 is a temperature but whats tha 0.5 ??

is it (T+0.5)/(T-0.5) = tempco? 

bye 
 Rene



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