Historic Transistor Photo
transistors were known as point contact, a name derived from the fact that
the collector and emitter connections of the transistor were formed using
sharpened metal points, pressed into contact with the germanium base block.
(See Bell Labs TYPE
A Transistor for a detailed discussion). Point contact transistors had many problems, including
mechanical and thermal instability, a high level of noise and poor
manufacturability. Many companies
experimented with making point contact devices, and some companies offered commercial
versions in limited quantities. Motorola briefly experimented with point contact transistor
technology in the early 1950s, before quickly moving on to become a major
supplier of alloy junction germanium power transistors in the late 1950s. The EP-7 units shown above are
experimental point contact transistors developed by Motorola in the early
1950s. These devices appear to be
hand-built. Note the plug of solder
on the side of the case in each unit shown above. This technique was likely used to cover a hole that was
required to allow physical adjustment of the point contacts to achieve best
performance. There is no record of
Motorola point contact transistors being offered for commercial sale.
© 2005 by Jack Ward. All Rights Reserved.