sawtooth vco schematic in trade journal

[Mike Granger]

There is also an interesting design idea that might be of interest to those who
have access to a scope. The November 2, 1998 excerpt contains an article on
building a low cost transistor matching circuit based on a single quad op-amp.
The circuit measures the relative match of a pair of transistors, and displays
the results on the scope screen.If anyone builds it, please let us know how it
works.

I'm lucky to have a commercial curve tracer to use for this purpose. I used to
have to match batches of 5 transistors for temperature sensing purposes. Try
that sometime when you have sone time to kill!

Michael Lloyd wrote:

> Just letting folks know that the latest Electronic Design magazine (july 26,
> 1999) features a sawtooth/squarewave VCO in the "Ideas For Design" section.
> Here is a link that should get you to the article (but when I tried it,
> article wasn't up yet!)
> http://devel.penton.com/ed/Pages/sitepage/ed_acces/ideas4ds.htm
> Click on "Ideas For Design 7/26/99" on the right hand side of the page, then
> go to next article.
> It's simple (claims cost is ~$3.00), and uses a Maxim op amp and comparator,
> as well as a pair of 2N3904 transisitors as the active elements.
>
> Michael
> mlloyd1 at enteract.com