[sdiy] new Texas ic log102 ? log ratio amp

[Tim Ressel]

I've had really good luck with the heater servo design
a la AN299 from National Semi. I changed the design to
use a MAT04; it has good performance. I even ran it in
an environmental chamber. It held together over a wide
range. One can get low tempco resistors from Digi-key
or Mouser. Burr-brown, TI, Linear Tech and others make
really high accuracy, low drift opamps. One could even
use chopper amps for the expo converter, if one has
found a money tree   $$$$$$$$$$$$$$$$$$$$$$

--TR







--- patchell <patchell at silcom.com> wrote:
>     I just took a look at the data sheet. 
> Unfortuneatly, this device is
> not really suitable for our use :-(, even if it was
> reasonably priced.
> If the thing had more pins so that the parts were
> not committed to
> strictly use as a log amp, it could be used to
> generate exponential
> functions.  But, again, it is way too expensive. 
> You could probably do
> almost as good using a CA3046.
> 
> Peter M Blackett wrote:
> 
> > Hi,
> > just noticed the LOG102 ic in the latest edition
> of Texas instruments
> > newsletter .[techinnovations11   ]
> > I don't know if this would be a posibility to be
> used in place of the
> > matched pair and tempco resistor in the vco design
> ?
> > I guess its the drift with temperature that is
> important .
> > regards Peter
> 
> --
>  -Jim
> ------------------------------------------------
> * Visit:http://www.silcom.com/~patchell/
> *-----------------------------------------------
> *I'm sure glad Merry Christmas comes just once a
> year
> * -Yogi Yorgensen
> ------------------------------------------------
> 
> 


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