PAiA VCO

[tomg]

Hi List,

I don't think thermal contact to the 13700 is necessary, maybe
the pnp's don't even have to touch...just match.. It looks as if
it's a servo controlled VCO. I may be giving John too much
credit. A list member came up with a FET servo...like last year
sometime? But using the diode in a dual OTA....now that's
original! Hell who knows people get to the same place by going
different roads all the time.

I also think that pnp pair is a dead giveaway as to the form the
rest of the VCO takes....;-)

I think John said that 1/T(temperature)  is theoretically  the
correct value to use when compensating for the affect temperature
drift  has on the normally used scheme of hooking a pair of transistors
to a vco and that  tempco resistors are almost correct but not
quite.  John wouldn't say something like that if it was not true. I
don't really know for sure, tempcos seem to work fine to my ears.
But then he said that too didn't he.

Tom


>
> Hi all,
>
> I'm quite unsure if I got how it works.
>
> I just don't see how that arrangement realizes a temperature dependant
> scale factor (gain). I can only imagine that this is doing some detuning in
> order to roughly compensate for the expected drift.
>
> I find the explanations on the FAQ page confusing, tempcos must be
> proportional to T in order to compensate for 1/T since that cancels out
> when you multiply.
>
> Oh, just in case anyone is still confused about tempcos. Check out:
> http://www.uni-bonn.de/~uzs159/expo_tutorial/index.html
>
> Bye,
>  René
>
> At 15:30 07.08.00 -0700, John Speth wrote:
> >     >       It
> >> might take me a
> >>  It sure makes the
> >> one I came up with look overly complicated.
> >>
> >>     I have to hand it to John Simonton, he can really come up with
> >> simpler solution.
> >>
> >>     -Jim
> >>
> >> Steve Ridley wrote:
> >>
> >>> Just (?) appeared at www.paia.com, the new dual VCO
> >>>  Very odd temperature compensation...   Doesn't the detection element
> >need to be in close thermal sync with the device it needs to compensate in
> >order for thermal compensation to work?  John Speth
> >Molectron Detector, Inc.
> >http://www.molectron.com
> >mailto:johns at molectron.com
> --
> uzs159 at uni-bonn.de
> http://www.uni-bonn.de/~uzs159
>
>
>