[sdiy] More VCO fun

[David G. Dixon]

> 3 -- The 2N4391 is *not* a low cutoff device.  The pinchoff is speced at 4
> to10V, and the units I have are close to 10V.  The comparator output is
> not -12V, it's closer to -11V, so the switch is *not* in deep depletion.

The 2N5485 that I'm using is, however (-0.5V to -4.0V), which is probably
what Achim was referring to.  One of these days, when I need more than a few
cents' worth of stuff to order from Digikey, I'll get some '4391s.