On Mon, 19 Mar 2007 16:25:26 -0500, "Anthony Fremont"
wrote:

Tam/WB2TT wrote:
"Anthony Fremont" wrote in message

I have never seen clipping. These things are supposed to limit in
cutoff, not saturation. As the signal build up, the conduction angle
gets smaller and smaller until the device runs out of gain. That is
another way of saying that the DC value of the gate voltage gets more
negative the bigger the amplitude. This works out automatically with
a JFET. You need about 10K - 100K DC resistance from gate to ground.
Using a bipolar transistor is not a good idea.

I was wondering about the load that a bipolar would present. I will see if
I can find a JFET in my junk pile, thank you. :-)

Without going to the purity levels that Tom requires, I've always found that
bipolars can be used to produce a fairly reasonable "visibly sinusoidal" (see
note) waveform. Follow the oscillator with an amplifier stage which drives a
limiter/clipper, and use that to control a gain element in the oscillator. It's
like the incandescent non-linearity arrangement except the oscillator stage
waveform remains fairly clean.

(Note: Harmonic distortion not readily discernible on a CRO)