Doepfer

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