Jerry Suran – The Story of the Unijunction Transistor 


Oral History – Jerry Suran (Continued)








Shown above are various prototype, pre-production and commercial versions of early General Electric unijunction transistors.  The two leftmost units are germanium prototypes from 1953/54.  Beginning in 1956, silicon was used instead of germanium for unijunction device fabrication.  The type “ZJ-14” shown above represents an early silicon pre-production unit and was the precursor of the commercial type 4JD5A1, which was introduced by GE in 1957. Standard JETEC “2N” designations were established by GE for unijunction transistors in the late 1950s, with the series 2N489, 2N490, 2N491, 2N492, 2N493 and 2N494. These were all silicon unijunction devices, with differing performance characteristics.  The earliest versions used a blue metal case (the 2N491 shown above is dated 1961). The later versions had a black metal case (the 2N489 shown above is dated 1963). The 2N489-494 series was established as a Mil-Standard type device.


General Electric was the primary manufacturer of unijunction transistors throughout the 1950s and 1960s, with Texas Instruments and Motorola providing second source types.  These original unijunctions were known as “bar-type”, based on the construction process using a single bar of silicon.  As additional transistor manufacturing processes were developed in the industry, some of these techniques were applied to unijunction types.  Shown on the left is an example of low cost planar unijunctions developed in the 1960s.



Go To Suran Oral History, Page 10

COPYRIGHT © 2005 by Jack Ward.  All Rights Reserved.  http://www.transistormuseum.com/