A SURVEY OF EARLY POWER TRANSISTORS

by Joe A. Knight

SYLVANIA 1950s GERMANIUM POWER TRANSISTORS

 

 

ABOVE, L-to-R:    By mid-1956 Sylvania had released it's first TO-3 PNP Ge type, the "2N242" (first item in top and bottom row), liberally rated at 25 watts of dissipated power.  They promoted it specifically as a 'hybrid' power transistor for use in car radios along with Sylvania tubes of course.   Like some other manufacturers, Sylvania used an 'in-house' numbering system for devices they likely used for their own products or special customers.  The next two TO-3 items reflect that numbering system, the "GT 900" and the "GT 912" with their corresponding cut-open versions shown below.  It is likely that some manufacturers often had their own numbered transistor items available for use before they had gotten the official RETMA registered 2NXXX numbers.  Upon close examination can also be seen the tiny welded seam around the copper top edge, distinctive to Sylvania's manufacturing process.   By the end of 1956 Sylvania had also released another PNP Ge TO-3 device, the "2N296".  This was closely followed by the PNP "2N307", last top item and the PNP "2N307A" (like RCA) in early 1957, now rated at 15 watts.  A little later in 1957 Sylvania released a TO-3 complementary pair, the PNP "2N325" and the NPN "2N326" which allowed for more modern output circuit designs.  These are more conservatively rated at 12 and 7 watts respectively.  The last item, bottom row, the "SYL 998", now is made with the curved rounded ends around the copper top.  This was Sylvania's unique factory design, which came out about 1959, and helps to distinguish their devices from others.   By the end of 1957 Sylvania had released no more new power transistor devices.  However, by 1958, they did become a second-source supplier for many other manufacturers’ output and small-signal devices and successfully did so for many years.  They must have felt this was their true calling and so ended a fine chapter in one of the true pioneers of Power Transistor technology.

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Joe A. Knight Early Power Transistor History – SYLVANIA Page 5