A SURVEY OF EARLY POWER TRANSISTORS

by Joe A. Knight

RCA 1950s GERMANIUM POWER TRANSISTORS

 

RCA, next to Bell Labs, had the largest research labs in the electronics industry in terms of size and people.   While not only being the largest manufacturer of electronic goods and appliances in the world they also owned the second largest number of semiconductor patents, again next to Bell Labs.  RCA had technology licensees since the early days of the vacuum tube as a result of controlling most of the early G.E. and Westinghouse tube patents.  And as they began to develop semiconductor technology, RCA would again license this know-how to whoever wanted it, for a price.  And including I am sure, a number of lesser electronic manufacturers who could not afford the huge research costs but needed to quickly get aboard the 

semiconductor bandwagon.  So it was that in November of 1952, much like Western Electric and BTL had done the year before, RCA held a Symposium for their licensees at the David Sarnoff Research Center to show them the future potential of transistor manufacturing and the vast world of possible applications.  Shown were early RCA prototypes of a portable TV, a portable AM radio, a portable phonograph, a portable FM radio, a wireless microphone, a musical keyboard and much more.  This was quite an imposing array at a time when most everyone else had no product development to show at all.  RCA also displayed the new transistor devices they were working on, both point-contact and junction types,  that were available then and in the near future.  Some of these new experimental junction types, shown below, were specifically designed for handling higher power output in some of these new applications.

 

 

ABOVE, L-to-R:  Again, all these from November, 1952.  The first two power transistors were designed with the concept of attaching additional metal radiating surface so as to conduct more heat away from the internal elements.  The third device is built with the junction structure attached to the inside top of a metal shell 'cup', 

again to quickly conduct more heat away from the junction elements.  The last interesting item, a liquid-filled device, uses a low viscosity fluid that would circulate by heat convection around the interior elements and so conduct away the heat to the exterior metal shell.  However, the most successfully fluid tried was Toluene.  Thusly, the whole concept of having to use inflammable fluids eventually ended this device.  No doubt even the RCA lawyers would never have slept at night if this device had ever gone into wide production.

 

So in 1953 RCA settled on the metal shell 'cup' design as having the most efficient heat conduction design with just over 1 watt of dissipation. These PNP devices could be used in Class A circuit designs or push-pull Class B circuits.  Additionally, RCA began looking at PNP-NPN "complementary- symmetry" output designs way back then.

 

 

 

 

 

 

Go To RCA Early Power Transistors, Page 2

 

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Joe A. Knight Early Power Transistor History – RCA