[sdiy] CA3046 Heater / Substrate Question

Bert Vermeulen bl.vermeulen at gmail.com
Fri May 6 15:32:43 CEST 2016


see datasheet 3046
Operating Temperature Range −40°C to +85°C

2016-05-06 14:14 GMT+02:00 Steve <sleepy_dog at gmx.de>:

> I've never done this, but do you really need 65°C?
> Wouldn't 40..45°C suffice? And you could perhaps put some thermally
> isolating foam around the IC, if the layout allows it? Then you'd not need
> to heat so much to be stronger than the surrounding heat I guess.
> Also... if the thing takes a minute to be operational, I personally
> couldn't care less, the guitarist also needs to heat up his gear :-)
>
> Steve
>
>
>
> *Von:* "Nils Pipenbrinck" <n.pipenbrinck at hilbert-space.de>
> *An:* synth-diy at dropmix.xs4all.nl
> *Betreff:* Re: [sdiy] CA3046 Heater / Substrate Question
> [...]
>
> > BTW, "better" is an enemy of "good". What is wrong with just 1
> > transistor heater?
>
> There is nothing wrong with it, but it's not ideal because the 1
> transistor heater can only dissipate 300mW. The cooling of the package
> takes away a big chunk of the energy we put into heating. So reaching
> tuning stability is slower than it could be.
>
>
> I did some measurements yesterday, measuring the Vbe drop directly while
> heating with two different target temperatures. I faked a bit, left the
> substrate transistor connected as usual and used one of the matched pair
> transistors as my second heater:
>
> http://torus.untergrund.net/synth/heater_65deg.png
>
> Here I aim at 65°C. You'll see that the two transistor circuit reaches
> stability after 4 seconds while the one transistor circuit needs about
> 100 seconds:
>
> http://torus.untergrund.net/synth/heater_90deg.png
>
> Here I aim at about 90°C. The two trannie method reaches stability after
> half a minute while the single transistor never reaches it's target
> temperature and asymptotically drifts to somewhere around 70°
>
>
> I think this is a great improvement over the one transistor circuit, and
> the substrate transistor is unused, so why not use it as a second heater?
>
>
> Best,
> Nils
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