[NewCandle] Parasitic Cap Charging

[George Holz]

Hi all,
 
John W. wrote:
>My claim was that I couldn't think of a way to make a (OK!) 
>*differential* negative resistance which works down to DC using a single 
>BJT.

Many NPN bipolar junction transistors will oscillate at 
BVceo with just two connections and an open base.
This is an avlanche mode negative resistance.
In most transistors the amplitude of the oscillation is
only about 20 percent of BVcbo.
Transistors designed to maximize the avalanche mode
will transition all the way down to Vsat when the
the Vceo is reached.
Some standard planar transistors will also exhibit the
large amplitude avalanche mode. The mode
is enhanced in high current gain, high frequency and
high voltage transistors. The transition to low voltage
is extremely fast, usually well under 10 ns. A small capacitor
from collector to emitter encourages the avalanche mode.
Too large a capacitor will damage the transistor.
I have used transistors specified for this mode as well
as standard  planar transistors selected for this mode 
using a curve tracer. 

It is possible that Ron's SEC mode is related to the
avalanche negative resistance breakdown.
I hope  to build hardware to test Parasitic Cap.
Charging soon. 

Very interesting experiments Ron!

George Holz
Varitronics Systems