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Oral History – Norm Ditrick (Continued)
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The first devices we made were
point contact transistors. These
were interesting devices. I think
that a few were actually put on the market, but I doubt they lasted very
long because these were very unstable.
I remember personally constructing quite a few of these transistors
myself, and then testing. There was
a process called forming which you had to do to get these things to work –
it involved applying a series of electrical pulses. I remember well doing much of the actual
assembly of these point contact transistors, along with a woman named
Margaret Deavy. She was already involved
in building these when I joined, and I learned from her how to make them. I think we must have made a few hundred
while I was involved in the program.
As I said, these were
commercialized. The type 2N32 was
spec’d as an amplifier and the 2N33 was intended as an oscillator – during
forming, we were able to pulse the 2N33 types to have a higher gain, and
this higher gain allowed for instability/oscillator function. We used handwritten red lettering to
identify the type and serial number of these point contact transistors
during development.
This work required extremely fine
manual manipulation, and so I decided to practice my skills by writing the
Lord’s Prayer on the head of a pin.
I made five or six of these, and was able to inscribe the complete
Lord’s Prayer in the very small area of a pin’s head. I obviously had to use a microscope and
extreme patience, but I was able to do it.
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Oral History – Norm Ditrick (Continued)
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Anyone who was actually
building the point contact transistors had to have great dexterity, because
it was necessary to move the small points “just so”.
We also worked on the first
RCA junction transistors, which were commercialized as the 2N34 and
2N35. I remember working on the
2N34, which was the PNP, although I don’t think I worked on the NPN 2N35. At some point, I went to the RCA Labs in
Princeton to work with Charlie Mueller on some developmental high frequency
junction transistors. At this time, “high frequency” meant IF frequency for
radios. The original junction
transistors would only work at audio frequencies. Working with Charlie, we got the transistors to function all
the way up to 2 MHZ, which was good enough for the standard AM radio. We accomplished this by varying the size
of the alloyed indium dots and by changing the physical structure of the
device to reduce the parasitic resistance. During this time I developed a technique which later was the
basis for one of my patents – we developed a technique to wet the indium
dots before alloying, and this improved the high frequency performance.
We started work on what were
called drift transistors next, which was a specialized junction transistor
that would perform up to 30 MHZ – 50 MHZ., which was good enough for
shortwave radio applications. I did
this work with another engineer named Aaron Kestenbaum.
Go
To Ditrick Oral History, Page 3
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