TRANSISTOR MUSEUM™  

Historic Transistor Photo Gallery

Photo Essay – Bell Labs Type A

 

           

  Photo Courtesy Bob McGarrah

 

         

   Power Versions of Type A Transistor

 

Photo Essay Commentary

Another unique aspect of early point contact transistors was the need to supply an adjustment hole in the side of the case to allow access to the area where the two point contacts are pressed against the germanium block.  This was necessary because actual electrical performance of the transistor could best be adjusted by physically moving the point contacts over the germanium surface, while monitoring electrical performance.  The Type A transistor was originally developed with a hole on each side of the case (see photo at top left), apparently to accommodate extensive adjustment.  These early point contact transistors performed erratically, and with parameters which compared unfavorably to vacuum tube technology.  The photo on the right, from [3], illustrates some unusual techniques of the time which were used to enhance the power handling capabilities of the Type A transistors – “Higher output can also be obtained by increasing the permissible collector dissipation.   This has been accomplished by using a thin wafer of germanium directly soldered to a copper base equipped with suitable fins… An increase in allowable dissipation from 200 to 600 milliwatts has been thereby obtained.”

 

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