[R-390] Nixie Tube Freq Readout

[2002tii]

Drew wrote:

>Are tunnel diodes even manufactured anymore?  Methinks that they are 
>only available as NOS now.  The tunnel diode - that miracle device 
>whose miracle never materialized.

They are in limited production by M-Pulse and Metelics, and perhaps 
others, still used for very fast (picosecond) pulse generators, 
high-microwave detectors, and in some military and aerospace rad-hard 
applications.  The technology is also being explored to raise the 
speed of solid-state logic.

As far as the miracle not materializing, the devices are good at what 
they are good at, but there was a bunch of hype about what they might 
be capable of (fueled in part by the award of a Nobel prize to the 
inventor, Leo Esaki, who did the work at Sony but had moved to IBM by 
the time of the award, and in part by the slugishness of the 
transistors of the day and the hopes of engineers who dreamed of GHz 
circuitry).  Negative resistance is an intriguing and useful 
property, but it does not lend itself well to producing power gain, 
and the lack of separate input and output ports further complicates 
the use of tunnel diodes as amplifiers.  So, to the extent that folks 
hoped to use them as amplifiers, that hope was not well borne out in 
practice.  Also, they are hard to integrate with other circuitry on a 
chip, a problem that has been addressed by the advent of resonant 
tunneling diodes.

Best regards,

Don