[sdiy] uA726, heated pairs...

[Gene Stopp]

BTW the Voyager uses MAT-04 per VCO, which I would guess is the expo. I have
not felt them during operation to see if they are oven-ized. Interestingly
enough there is one tempco in there. Maybe one tempco for all three VCO's?
Since it's the scale factor that's getting tempco'ed, and all 3 VCO's are
tracking the CV source, does this not sound like an elegant way to reduce
the tempco count?

- Gene


-----Original Message-----
From: Tim Ressel [mailto:madhun2001 at yahoo.com]
Sent: Friday, August 08, 2003 11:12 AM
To: Grant Richter; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] uA726, heated pairs...


Grant,

The substrate needs to be connected to the lowest
voltage the IC will see. In my case I didn't see that
part of the datasheet until after I had wired the
circuit. So I made that transistor unused and replaced
it with an external 2N4401. Pin 13 (substrate) is tied
to -V. The 2N4401 replaces the transistor that serves
as a clamp for the output transistor. I used the same
scheme when I used a MAT04 which has only 4
transistors.

--tr


--- Grant Richter <grichter at asapnet.net> wrote:
> Do you remember what you did with the substrate pin?
> 
> open, ground or -15V?
> 
> > From: Tim Ressel <madhun2001 at yahoo.com>
> > Date: Fri, 8 Aug 2003 09:23:59 -0700 (PDT)
> > To: Grant Richter <grichter at asapnet.net>, Keith
> Daniel <ensign7 at e-scape.net>,
> > synth-diy at dropmix.xs4all.nl
> > Subject: Re: [sdiy] uA726, heated pairs...
> > 
> > Yo,
> > 
> > I use the heater circuit from AN299 on my VCOs.
> One
> > uses a 3046, the other uses a MAT04. It works as
> > advertised. I checked the circuit in an
> environmental
> > chamber so I could verify operation up to +40C.
> > 
> > --tr
> > 
> > 
> > --- Grant Richter <grichter at asapnet.net> wrote:
> >>> There is the little known National Semiconductor
> >> app note AN-299 (1986?),
> >>> where an LM3046 transistor array is used to
> >> provide a heated pair for a VCO.
> >>> 
> >>> I've tried it, but it seems to me that there was
> a
> >> change in chip manufacture,
> >>> and it doesn't work as advertised. The substrate
> >> pin is the problem.
> >>> 
> >> 
> >> Just a couple stray thoughts...
> >> 
> >> The ap note doesn't specify the pin out on the
> >> CA3046. You could probably
> >> get it to work by trying different combinations
> of
> >> heater and sensor
> >> transistor.
> >> 
> >> Also, the substrate connects to the most negative
> >> voltage used, in this
> >> case, it looks like ground and not -15V.
> >> 
> >> For a working example, see the Moog "Source"
> service
> >> manual which used a
> >> thermostated CA3046 for the expo-converter. The
> >> Serge NTO and PCO also use a
> >> heated CA3046.
> >> 
> > 
> > 
> > __________________________________
> > Do you Yahoo!?
> > Yahoo! SiteBuilder - Free, easy-to-use web site
> design software
> > http://sitebuilder.yahoo.com
> > 
> 


__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com