TRANSISTOR MUSEUM ™  

Historic Transistor Construction Project  

 

 

This is a photo of a Western electric 2N23 point contact transistor, which is the type used in this project. A few companies commercially produced point contact transistors, but only Western Electric entered large scale production.  The above unit is from 1953.  The case is a white plastic semicircular disk, approximately ¼” in diameter.  The thick metal lead is the base connection and the two fine wires are the collector (marked with a dot on the case) and emitter.  The wires are extremely fragile and working with this transistor type is difficult. 

 

The photo below is a top view of the modern preamplifier designed and built by Gerry Friton, using two 2N23 point contact transistors – these can be seen in the center of the unit as small white plastic disks.  Gerry’s preamp is powered by three AA cells (4.5V). 

 

 

 

Modern Audio Preamplifier Using

Historic Point Contact Transistors 

 

HISTORIC NOTES

The first transistor type invented was known as point contact – this technology appeared in the late 1940s, based on pioneering research conducted at Bell Labs.  These first transistors were very crude and required precise mechanical adjustment of two fine wires (point contacts) pressed down on top of a germanium block.  There were many problems with point contact technology, including erratic behavior, sensitivity to physical shock and temperature, and a high inherent noise level.  By the early 1950s, newer transistor types (grown junction and alloy junction) were developed to address some of these problems.  Circuit development and design with point contact transistors lasted only for a very few years (1947 through the early 1950s), as this unique technology was quickly superceded.  

MODERN CIRCUIT

Gerry Friton, a talented professional electrical engineer, recently developed a modern point contact transistor circuit – an audio preamplifier.  This may be the first documented point contact transistor project in almost 50 years!  Use the following link for more details and the schematic of this exciting project:

  Point Contact Transistor Project - Page 2

 

Copyright © 2002 by Jack Ward

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