Transistor Museum Early Germanium Power Transistor History by Joe Knight BTL Western Electric Page 22

A SURVEY OF EARLY POWER TRANSISTORS

by Joe Knight

THE POWER TRANSISTOR

BELL TELEPHONE LABS AND WESTERN ELECTRIC

While Bell Labs was developing their own telephone system updated high power WE 9A transistors, they also developed a higher speed core-memory driver called the WE 2075 (no picture), a PNP Germanium Alloy Junction medium-power transistor, likely from 1958.

By the middle of 1959 BTL had finished a JEDEC (the old RETMA) registered version of their own WE 9D core-memory driver, which could then be sourced for their government and military customers and contracts. This device was called the WE 2N528 (derived from the WE 2075) and is shown below. It too was a PNP Germanium Alloy Junction medium-power device suitable for high-speed switching as a core-memory driver, rated at about 3 watts of dissipated power. It was switching at less than 1 micro-second - pretty fast at that time. The exhaust tube tip is on the top but was eliminated a few years later as it was for most all WE Power Transistors. The stepped shoulder top cover allowed for keeping the overall profile lower than on the other previous devices. It has the same electrical characteristics as its predecessors, the WE GA-53242 and GF-45017.

The cut-open WE 2N528 at right shows the compact element construction (the bottom corner of the square Germanium pellet is broken off) necessary to achieve the higher switching speeds needed for this device application. The bottom shell has three thin connecting wires for circuit installation (w/no stud), the same as first used on the WE GF-45017 design shown on Page 16. This was the first use then of this new WE semiconductor enclosure standard, called the 'TO-38' type, also registered in July of 1959 by Western Electric. The 'TO-38' enclosure would be used by WE for several more years of Power Transistor development.

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Joe Knight Early Power Transistor History – BTL/WESTERN ELECTRIC Page 22