Compensated Exp generators

Joachim Verghese jocke at netcontrol.fi
Tue Jun 6 12:13:50 CEST 1995


On Tue, 6 Jun 1995, Haible_Juergen#Tel2743 wrote:

> No. The capacitor is charged by the constant current from the
> expo converter, just as before. The resistor is just in series of the
> cap and doesn't change the current value at all. The only thing
> that the resistor does, is adding the same offset voltage that You
> are generating by other means (only at the other input of the
> comparator).
> Thinking of it a second time, I find that it also has the same side
> effect like You described (slight change in amplitude with frequency).
> The only remaining advantage is that this single-resistor addition
> is probably the most simple method to get the desired result.

I'd just like to add that the Moog Taurus oscillators utilised this
technique, and the service manual gives a thorough explanation of
how it works. (The Taurus VCOs are V/Hz, but of course, that doesn't
affect the design of the sawtooth generating intergrator).

-joachim



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