yes tim, thx for the reply. thus far, i've only used transistors as
crude pre-amp circuits (for piezo disks) and white noise. your
explanation is good.

transitors, i think, are little demonstrators for quantum physics.
strange, mysterious little things they are!

----tom

--- In Doepfer_a100@yahoogroups.com , "Tim Stinchcombe" <timothy@...>
wrote:

>
> Hi Tom,
>
> > this is cool. without excessive nerdery, could you tell me briefly
> > why the jFET does not need power i'm new to circuitry and i'm
> > curious.
>
> Transistors in general (BJTs and MOSFETs, as well as JFETs) have
> several different operating regions, which display different
> characteristics depending on the voltages across/currents through
> them. When used as an amplifier say, a transistor needs to be placed
> in an appropriate region for correct operation, and this is done by
> supplying power via various resistors etc, which is called 'biasing' -
> when the signal is applied to it, the transistor will operate fairly
> close to this 'quiescent point'. In this sine waveshaping circuit the
> JFET is not operated like that at all: the signal voltage itself is
> taking the JFET through it's different regions, and it is the
> characteristics of these that cause the tri to be turned into a sine.
> The curious thing is that the positive and negative swings of the
> triangle take the JFET through two extremes of its operation, which
> have quite different characteristics, and yet both end up doing
> essentially the same thing - rounding-off the point of the triangle!
>
> I'm not that experienced with JFETs (they are pretty funny beasts to
> work with), so I'm hoping that when I eventually get the original
> paper in a few weeks time it will reveal the secret's of the circuits
> operation! I've also just updated the page to include the two
> trimpots I left off originally.
>
> I hope that is a lucid enough explanation!
>
> Tim
>