[NewCandle] Parasitic Cap Charging

[Keith Nagel]

Hi John + Ron,

While I can't now go to Ron's website to see the circuit again, I gather
from the email that he's got some kind of colpitts oscillator going on. 

http://en.wikipedia.org/wiki/Colpitts_oscillator

This oscillator indeed has a negative resistance characteristic, and
fills the claim of a circuit with such using only one BJT.

Not too quibble over nomenclature, but what you (John)
are describing is a negative differential
resistance. A true negative resistance is one in which energy is
inserted into the circuit through the "resistance". An old friend of
mine humorously referred to this as "joule cooling". I have built
such a circuit, but before you guys get too excited, the energy source
doing the "inserting" was a DC pulse. From the point of view of
the circuit, there would be a positive current and a negative voltage,
a true negative resistance. When this circuit element was put into
a passive LC network, the whole circuit would ring up at the resonant
frequency at the expense of the DC driving pulse. It's tempting
to write this up for the website, but I did this work years ago
so I don't have pics of the device, just the scope shots. 
   
Not to put words in Ron's mouth, but I think when he asks you to
forget everything you know and build the circuit what's he's
doing in effect is to say, "look, I could spend a month
arguing with you about this thing, but if
you build a copy and play with it most of the discussion can
be avoided and we'll be on the same page pretty quickly". It
is in fact the quality that makes Ron welcome here; his
constant exhorting of people to actually build up some hardware
and play with it. I would take his advice; the circuits he's
working with are simple to build, but can be devilish to
characterize because of the frequencies he's working at. As
you (John) already surmised, stray capacities come into play
in many of Ron's circuits, and distributed capacities and inductances
also matter greatly at these high frequencies. 

Why don't we all do something together? Ron, perhaps you could
cook up _one_ circuit that best shows the effects of interest to
you. I have all the stuff to build up most of what you've been
describing ( save the LEDs but I don't think your latest circuit
used them ). John should do likewise. Ron, I'm afraid that I
can't do a big exploration with you on this, too many irons
on the fire already, but I can certainly carve out enough time
to do one circuit considering all the good work you've been doing.
How's that sound? 

K.