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You seem to understand electronics pretty well... You might want
to look up one of the two transistor circuits that behave like a
tunnel diode, build one, and study it. It's probably better to
just consider it magic.

It probably didn't help the tunnel diode's understandability to
name it after the physics property that makes it work. I think
a better name would have been a "trigger diode".

It also doesn't help that the curves that are typically published
are more a manifestation of the curve tracer's very slow speed
capabilities than they are of what the tunnel diode is really doing.

More on that later...

Imagine a part that as you increased the voltage across the part,
the current rises, and rises, and rises, then at a trigger voltage,
the current instantly drops to a near zero lower value... like you
burned out a fuse.

As you let the voltage continue inching its way up, the current stays
low, until it reaches a threshold where it once again starts to rise
endlessly and rapidly, like a conducting diode.

Here's where the typical I/V curves fail you: The current drop at the
tunnel diode's trigger voltage is so fast that you never would be
able to see it on any curve tracer without a ton of intrinsic capacitance
(inside of the curve tracer) slowing it down.

A real curve trace of a tunnel diode would show the trace rising to
the trigger voltage, and then reappearing at the near zero triggered
voltage. It would be discontinuous. There is no there there.

Thanks to magic, the I/V curve is reversible. So, there is really
two trigger voltages: one going up, and one going down.

Through a variety of tricky tricks, you can exploit those sudden
changes in current to produce very pretty trigger pulses. And use
those pretty trigger pulses to trip flip-flops, and multivibrators.

-Chuck Harris

Jeff Urban wrote: