A SURVEY OF EARLY POWER TRANSISTORS

by Joe A. Knight

SYLVANIA 1950s GERMANIUM POWER TRANSISTORS

 

Sylvania was one of those large early electrical manufacturing corporations, originally making incandescent lamps and later vacuum tubes, such that by the early 1950's they were well over 50 years old.  Similar to some of the other 'Giants', like RCA and Raytheon, they manufactured electronic parts, materials and consumer appliances.  During WW2, Sylvania was the leader, along with Bell Labs, in developing crystal diodes for military radar and UHF research and development.  So it was, when Bell Labs announced the Transistor in 1948, that Sylvania had all the necessary research and production facilities to jump right into the semiconductor business.  And in 1949 Sylvania became one of the first to produce a commercially available transistor, the point-contact cartridge type "GT-372".   They would later become instrumental in the field of Power Transistors such that by early 1956 Sylvania had more power devices available than any other manufacturer.

 

While Sylvania likely had cross-licensing agreements with other vacuum tube designer-manufacturers, as was common to the industry, it apparently didn't take them long to do the same with other transistor companies.  While RCA was the first to make their famous 2N32-2N35 transistor series available in early 1953, Sylvania had announced by mid-1953 their own available production of the RCA 2N32 point-contact type and the 2N34 junction type (and later the 2N35 junction type).  Theirs however were contained in hermetically sealed metal cases, which was a major problem for the RCA transistors as they were only resin sealed from the detrimental effects of outside moisture.  Thus, in addition to their own semiconductor product development, began a long history of Sylvania becoming a second-source for many other manufacturers small-signal and power devices.

 

In mid-1954 Sylvania announced their first Power Transistor called the "2N68" (shown below), which was also their own first semiconductor product registered with RETMA (later called JEDEC).  This device was rated at just 1.5 watts of dissipated power.  It appears that with their ability to license other small-signal developed products Sylvania could focus more on the area of Power Transistor research and production.

    

 

As can be seen from the ad picture (shown at left), this first "2N68"  is unlike the later ones we normally associate with this particular transistor number. (Anyone ever seen one of these?)  Maybe in their eagerness to come out with a new product, where only months before Honeywell had released their first Power Transistor (the 2N57), Sylvania came to market too soon with this device.  Consequently, it may have only been in limited pilot production before the competition brought about it's demise.

 

Apparently, either this particular constructed device didn't perform all that well or didn't really provide the power capability they wanted, as by the end of 1954 Sylvania changed to an altogether new power transistor design built with aluminum cooling fins as shown below. The 2N68 power transistor was a PNP Germanium device and they now have a threaded bolt hole on top for attachment to an external heat-sink for even greater dissipation.

Go To Sylvania Early Power Transistors, Page 2  

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Joe A. Knight Early Power Transistor History – SYLVANIA