[sdiy] PNP Matched problem...CA3096

[patchell]

"M. Falconi" wrote:

> Subject:
>     Date:
>          Fri, 04 Jan 2002 01:00:57 +0100
>    From:
>          "M. Falconi" <thermen at libero.it>
>
> Thanks at everyone for all answer about my question.
> I realized many problems with two matched PNP transistor in CA3096.
> Ach......Grrrr....Mmmmm
> I work with Electronotes VCO ( see schematics on
> http://homepage.mac.com/mauriziofalconi/pict/synth/vcoschem.html ),
> and the exponential converter work with PNP matched AD821 ( i no found
> this or similar pair ).
> Now i use  two 2N3906 "Home VBE Matching" but no good.
> Question: it's better a CA3096 temperature controlled or is more simple
> another patched transistor with 2K TempCo resistor?
> I see in Jim Patchell site a MAT 03, but is very difficult  for me in

    Actually, I have MAT04's.  For PNP's I have THAT120's (in stock until they
run out, they are no longer made).

>
> Italy found this transistor .
> I found a 1K TempCo resistor at Farnell in UK, but Farnell no near at my
> house....today the europe is still large...
>

    There are other alternatives to using TempCo resistors, but you still need a
pretty good set of transistors.  You should be able to use a matched pair of
2n3906's (I have used unmatched ones fairly succesfully as well).  You do
realize they must be glued together with epoxy in order to track well.

    Another good PNP choice is the 2sc1583 (did I get that number right?).

    Anyway, it is posible to use the reference transistor for a temp sensor and
to use that to control the gain of an OTA to do the temp compensation.

    If you look at http://www.silcom.com/~patchell/smb1/smb.pdf, on page 21 U94,
U90A, U92A/B and  U93C make up the expo converter/temp compensation, although,
this one is for NPN expo transistors.

    For PNP type transistor expo converters
http://www.silcom.com/~patchell/synthmodules/vocalfilter.pdf, Page 9 shows an
expo converter/temp compensation for PNP's (in fact, I used matched 2n3906's
here, no prob).  U20B, Q5,Q6, U24A make up the guts of the circuit.

>
> Thank for help
>
> Maurizio
>
> ----------------------------------------------------------------------------
>
> Thank you for visit my Theremin / Analog Synth amateur site
>
> ----   " OFFICINA ANALOGICA"  ----
>
> http://homepage.mac.com/mauriziofalconi/
>
> WELCOME!
>
> Maurizio Falconi - Siena - ITALY

--
 -Jim
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