A SURVEY OF EARLY POWER TRANSISTORS

by Joe Knight

GERMANIUM PRODUCTS CORP

1950s POWER TRANSISTORS

 

 

As we know Germanium Products Corp (GPC) was the first to produce a germanium junction transistor by the middle of 1952, only 1 year after Bell Labs announced the design concept.  Their first application was in the early Sonotone hearing aids.  While problematic, GPC went on for several years producing a variety of small signal transistors up to about 1956/1957.

 

In Lloyd Hunter's 1956 book, "Handbook of Semiconductor Electronics", chapter 9, he shows an excellent collection of early point-contact transistors, junction transistors and diodes from the time period of 1952 to late 1953/early 1954. The picture on page 9-4, at the bottom, also shows a rather large metal can encased device called the 'Germanium Products  RDX500 1/2 watt'.  The above series of semiconductor devices shows the likely development of this RDX 500 device, which, given it's inclusion in Hunter's book, would likely date this device to late 1953.

 

L-TO-R: The first item is one of the GPC first junction plastic encased transistors, the RD 2520, released in early 1953.  Other transistors from this same series were the RD 2517 (released in 1952) and the RD 2521(1953).  Later in 1953, another device was announced, the RD 2521.  All these early transistors were NPN Germanium grown-junction types.  (By 1954/1955, all of these transistors were available in small metal case versions with an A suffix, ala  RD2517A.)  Their early advertised power rating was only 50 milliwatts of dissipation.  However, by late 1953 GPC advertised their dissipation ratings at 150 mw.  This would seem to be a substantial increase in power ratings from what looked to be the same type of construction.  Likely they were feeling the pressure from their competition who were coming out with even higher power rated devices.   As we also know the early GPC transistors used in the hearing aids had a problem with moisture penetration, as did many other manufacturers.   Being only plastic encased, it didn't take too long for moisture to creep up the leads into the housing and contaminate the junction, effectively shorting it out. 

 

The next device shown is identical to the GPC "RDX 500" shown in Hunter's book.  This product would seem to be an outgrowth of GPC's attempt to be the first out with a truly high power (> 1/3 watt) output device as both RCA and W.E. were well on the way with their own versions by then.  Looking at the next item, an interior of a RDX 500, we can see inside the metal enclosure to what is actually a GPC 'RD25XX'  series device (without the black paint).  The same transistor thin wire leads now mount it onto a base with substantially thicker wire leads.  However, while GPC did nothing more than put a small transistor into a large sealed metal enclosure this device can now all of a sudden dissipate up to 500 milliwatts of power - a 10 fold increase.  Quite impressive one would have to say.   

Go To Germanium Products Corp Early Power Transistors, Page 2

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Joe Knight Early Power Transistor History – GERMANIUM PRODUCTS  CORP