9 Jul
2007
9 Jul
'07
10:02 p.m.
From: "Chuck Guzis" <cclist at
sydex.com>
On 9 Jul 2007 at 18:45, Dave McGuire wrote:
Hi
For those that want to play with the concept of a Tunnel Diode, one
can make a almost TD using two junction fets. You need a p and a
n channel fet. Place them such that the sources are crossed to the
gates. They will then act like a TD except that they will completely
turn off as the voltage increases. For the smaller TO-92 type fets,
they'll peak at around 1 to 1.5 milliamps. They will oscillate up to
a couple hundred Hz.
I built a FM jammer with a small trim cap, two fets, a coil, variable
resistor , bypass cap and a 9 volt battery.
For logic functions, they can be made into a stable two state element
by stacking 2 of these. One will have the higher voltage across it
while the other will have the lower voltage.
If you really want them to act like a TD, place a resistor in parallel
to give the final slope. It doesn't make them any better at doing
fun things but is closer the a real TD.
Dwight
_________________________________________________________________
http://im.live.com/messenger/im/home/?source=hmtextlinkjuly07
Relaxation oscillators are fun. I like the
UJT version as well,
though UJTs are getting harder to find than they once were. I have
two or three 2N2646 UJTs left.
I've still got about a dozen tunnel diodes sitting unsued in my desk
drawer. One of these days, I'm going to do something with at least
one of them.
Cheers,
Chuck