[sdiy] 1-quadrant multiplier with 2164

Guy McCusker guy.mccusker at gmail.com
Tue Jan 18 13:43:22 CET 2022

On Tue, Jan 18, 2022 at 11:27 AM Neil Johnson via Synth-diy <
synth-diy at synth-diy.org> wrote:

> The idea of quadrants is a 2-dimensional XY graph (there can be more
> dimensions, but let's stick to 2D for now).
> If you draw a big "+" on a sheet of paper, with the middle crossing as
> "0", then -x to +x on the horizontal, and -y to +y on the vertical, you now
> have the four quarters, or quadrants.
> - if both inputs are unipolar then the output will be unipolar and the
> transfer function is a line in one quadrant.  1-quadrant.
> - if one input is bipolar, e.g., typical audio signal with no DC, then the
> output function sits in two quadrants.  2-quadrant.
> - if both inputs are bipolar, then the output will occupy all four
> quadrants.  4-quadrant.

This is certainly true but note also the importance of zero when
multiplying. The zero signal stays zero no matter what you multiply by. In
Rutger's case that zero is in fact -5V, so the origin of Neil's graph
should be at -5V signal and zero control voltage. That is why the
level-shifting solution is so effective and it is also why I believe Rutger
is correct to call this a one quadrant multiplier.
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