Historic Transistor Photo Gallery

Photo Essay – Shockley 4 Layer Diodes





   Photo Courtesy Gene Weckler




Type 4N120D Shockley Diode



Photo Essay Commentary

These photos illustrate two of the various case styles used for Shockley diodes.  The leftmost unit is a high power device (4G200D), which is a 200 volt, 50 milliamp device that cost $40 in 1959. The unit on the right is a 4N120D, which is a lower power device that sold for approximately $8.  The “4N” numbering series appears to have been used for the earliest devices, with later devices labeled as “4E, F and G”.  The numbers following the type id were used to represent the switching voltage of the device, so that the 4G200D was a 200 volt device, and the 4N120D switched at 120 volts. See [1] for additional information regarding model numbers and performance.



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