[sdiy] CA3096 Temperature Controlled Question

[Scott Bernardi]

The pnp's in the CA3096 are lateral pnps and are pretty crappy - high rbe, low
early voltage, and Beta drops way down if you put more than a couple hundred uA
trough them. This makes them pretty poor for exponential converters or wide range
current mirrors, also (i.e., if you were thinking of using the npns for the
exponential converter and then mirroring the current with the pnps).
If you need good matched pnps, try the THAT-120 (4 matched dielectrically isolated
pnps). Available from Jim Patchell at
http://www.silcom.com/~patchell/parts/parts.html. He also sells the THAT-140 which
has two matched npns and two matched pnps in one package - all with good specs.

Grant Richter wrote:

> Hello,
>
> I have tried this approach. I noticed the PNP transistors in the CA3096 have
> a rather high Rbe and you may need quite a lot of compensation for the log
> converter. Assume you will need to use a Rossum compensation, a De Franco
> scheme will require up to 10K in series with the timing cap.
>
> The typical temperature for thermo stabilized dies is just above the highest
> ambient temperature expected. 130-140 degrees F is typical, watch out for
> oscillation in the thermal loop which will show up as pitch cycles. If the
> loop will not stabilize, use different transistors for heater and sensor.
>
> > From: "M. Falconi" <thermen at libero.it>
> > Reply-To: owner-synth-diy at dropmix.xs4all.nl
> > Date: Fri, 04 Jan 2002 01:23:56 +0100
> > To: synth-diy at dropmix.xs4all.nl
> > Subject: [sdiy] CA3096 Temperature Controlled Question
> >
> > I Built  temperature control as in National semic. AN-299 modified by
> > Rick Jansen.
> > I used a CA 3096 instead CA 3046, i need of two PNP/Matched transistor
> > for my log converter.
> > The circuit work well ! I test at 35 C° on the chip for many hours , all
> > ok.
> >
> > But i have a question: What is the correct temperature I will have work
> > the chips , for work my converter well and no burn the ic?
> >
> > Excuse me for my english
> >
> > Thank you
> >
> > Maurizio
> >
> > ----------------------------------------------------------------------------
> >
> > Thank you for visit my Theremin / Analog Synth amateur site
> >
> > ----   " OFFICINA ANALOGICA"  ----
> >
> > http://homepage.mac.com/mauriziofalconi/
> >
> > WELCOME!
> >
> > Maurizio Falconi - Siena - ITALY
> >
> >
> >

--
Scott Bernardi
sbernardi at attbi.com