[sdiy] Thought experiment...

[D A F]

Hi all,

I was taking a look at the schematic for the music from outer space VCO board, when I got an idea concerning a possible way to elliminate tempcos from VCO's.  I'm sure someone has probably thought of this (like 40 years ago) but in any case, here goes...   If you had a quad of matched transistors on a single substrate (such as in the new THAT 300 series), or at least two thermally coupled pairs, couldn't you send one pair a positive-going CV and the other pair a negative-going CV and then send the two outputs to a differential amplifier, such that only the difference signal would be amplified.  This would elliminate the change in current with temperature from the final output, because it would be equal in both pairs, assuming perfectly matched and thermally-coupled devices, and the diff amp would 'ignore' it.  Any thoughts?


Dave
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