Doepfer

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
>