Norman H. Ditrick


Oral History – Norm Ditrick (Continued)


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.





Oral History – Norm Ditrick (Continued)


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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