[sdiy] Fw: Reference stabilizes exponential current

[Jim Patchell]

    What he did is not all that different from experments that I have done, as
well as JH did.  The output of IC3 is proportional to temperature, and can be
used to control the gain of the expo driver.  The methodes that JH and myself
use don't require an extra transistor in expo array so that they could be used
with just matched pairs.  However, I have to say, if you are going to be using a
DAC to set the pitch of your VCO, the Bill Travis circuit does have a certain
apeal.

Craig Critchley wrote:

> The author of this article must be a nut for different ways to build an
> exponential converter.  I thought the name looked familiar from a recent
> Circuit Cellar article, from the September issue, and sure enough the name's
> the same.
>
> In the Circuit Cellar article, he uses two additional transistors in a
> ca3046 to heat the chip to a constant temperature.  In that article it was
> driving a 74hct4046 vco.  He claimed 4 decades of accuracy for it.
>
> It doesn't look like this article is online yet, but the Circuit Cellar
> archive only goes up to Aug. so maybe it will be available later.
>
>                             ...Craig
>
> ----- Original Message -----
> From: "Michael Lloyd" <mlloyd1 at enteract.com>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, October 31, 2001 6:20 PM
> Subject: [sdiy] Fw: Reference stabilizes exponential current
>
> ----- Original Message -----
> From: Michael Lloyd
> To: mlloyd
> Sent: Wednesday, October 31, 2001 2:59 PM
> Subject: Reference stabilizes exponential current
>
> http://www.e-insite.net/ednmag/index.asp?layout=article&stt=000&articleid=CA
> 178103&pubdate=10/25/2001