Transistor Museum Early Germanium Power Transistor History by Joe Knight Bendix

A SURVEY OF EARLY POWER TRANSISTORS

by Joe Knight

BENDIX 1950/1960s GERMANIUM POWER TRANSISTORS

As far as we can tell, Bendix was one of those manufacturers who only made large power transistors - no small signal types. A lot of their early efforts were focused on the emerging car radio audio amplifier market which attracted most of the other transistor designers at that time too.

Top Row:

In mid-1956 Bendix released their first TO-3 Germanium PNP type power audio transistors, the 2N234, the 2N235 (far right - also known as the in-house model B-111) and the 2N236, all rated at 25 watts dissipation. These early ones were unusual in that they had a small top-hat cover, which as it turns out is nothing more than a cover for the exhaust tip, shown in the far left developmental model, from early 1956. The one next to it shows the preproduction version with the top-hat cover over the tip. Most likely it may have been put there just to keep people from injuring themselves by scraping across the tip sharp edge. Or maybe they wanted one to think it was some kind of additional heat sink, ala the Amperex 2N115. Who knows??

Second Row:

Late in 1956 the Bendix 2N285 was released (This was also known as the in-house model B-112). The Bendix model 2N235A was also released late in 1956, also rated at 25 watts dissipation. (This was known as the in-house model B-104) The second one from the left is a 2N235B (hard to read red numbers), released in 1957. This one has a production code of '737' so we can see that by the second half of 1957 Bendix had finally done away with the top exhaust method of construction and thusly didn't need a top-hat cover any more. The unmarked far left item is an early production model of this change. The in-house transistors, model B-114 and B-121, were also released late in 1956. Also released by early 1957 were the 2N234A, the 2N236A, the 2N236B and the 2N285A.

Go To Bendix Early Power Transistors, Page 2

Joe Knight Early Power Transistor History – BENDIX