[sdiy] Linear current source - temperature compensation?

[Tim Ressel]

The linear portion of the expo convertor is not relying on a 
characteristic of the transistors that is temperature dependent so it 
should be fine. The will still be a little temperature drift because of 
the resistors, but that will be nowhere near the 3300ppm you get from 
transistors.

--tr



On 11/14/2016 11:17 AM, Justin Owen wrote:
> I went with the adapted Electronotes design because I'm using the 
> full, temperature compensated exponential version on another project - 
> it seemed like a good idea to stick with one circuit that I knew worked.
>
> The linear version I'm using is driving a VCA - so it's not pitch 
> critical and I'm not seeing any temperature effects under normal use 
> (unless e.g. I hold the circuit under a heater or some such...)
>
> ...but I was still curious if there was the possibility of temperature 
> compensation on the linear parts.
>
> Thanks,
>
> / J
>
> -----Original Message-----
> From: Nathan Trites [nathan at idmclassics.net]
> Received: 12.11.2016 18:37:15
> To: Justin Owen
> Cc: SDIY List
> Subject: Re: [sdiy] Linear current source - temperature compensation?
>
> Is there any reason for sticking with the electronotes design? If the
> tempcos are only there to compensate for the temperature effect of the
> transistors, if you do away with the transistor pair altogether theres no
> reason for them.
>
> - N
>
>
>
> On Sat, Nov 12, 2016 at 8:29 AM, Justin Owen <juzowen at gmail.com> wrote:
>
> > Hello,
> >
> > The classic Electronotes current source has a linear input. It's 
> possible
> > to chop out some of the exponential parts and just have a linear current
> > source based on that design - however, you lose the two standard Tempco
> > placement positions.
> >
> > So - is it possible to temperature compensate a linear-only current 
> source?
> >
> > 1) Please ignore the component values...
> > 2) I'm assuming the same temperature variation/dependance exists in the
> > linear version...
> >
> > http://www.sdiy.org/juz/source_exp.png - exponential
> >
> > http://www.sdiy.org/juz/source_lin.png - adapted to linear only
> >
> > Thanks,
> >
> > / Justin
> >
> >
> >
> > _______________________________________________
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> >
>
>
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-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com

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