MAT-02 and MAT-04

Tony Clark clark at andrews.edu
Thu Mar 16 18:33:47 CET 2000


> I am getting ready to try a scheme where two of the transistors in a MAT-04
> would be for a expo convertor, and the other two would be for a 
> heater, with one as a sensor and the other as the heating element. The 
> current specs are way down from the CA3046, so the heating will be 
> less. I may have to use an external resistor for heat, and perhaps go 
> to switching scheme instead of linear control.

   I tried this and never had much good success.  Because of the way the 
MAT-04 is layed out, choosing which transistors to use as the heating and 
sensing elements may play a huge role in how well it works.
   The transistors are layed out in a grid pattern.  So it would make 
sense to use opposite placed transistors so that there is even heating 
across the substrate as opposed to using side-by-side transistors.
   Again, I never could get the circuitry to really stabilize in a 
repeated fashion, so I gave up on that.  Perhaps you'll find a better 
method?  One thing to note, if you do use a switching heating style, be 
sure that the frequency is below audio rate as it will bleed into the 
expo-converter!
   The advantage of using a linear control is that there is no frequency 
to bleed across, but as I mentioned before, I found it to be extremely 
finickey to get working decently.  Your mileage may vary.

   Tony

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