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TRANSISTOR
MUSEUM Historic Transistor Photo
Gallery |
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HISTORIC
NOTES The earliest junction transistors performed better than the original point contact transistors in all respects except one – frequency response. Whether grown junction or alloy, the first junction transistors were very limited in terms in effective operating frequency. This limitation was overcome in a number of ways, including the use of a fourth electrode attached to the base of the transistor. By proper use of bias voltages on this additional lead, the transistor could be made to effectively operate up to 15MHZ, which was fairly impressive for this timeframe. Several companies offered these four lead (tetrode) transistors, including Western Electric (3N22), Texas Instruments (3N34/35) and GE (3N36/37). By the early 1960s, other transistor technologies, such as MDT/MADT, mesa and planar were available which operated into the 100s of MHZ and the tetrodes were obsolete. Western Electric transistors were not typically sold commercially, and were available only for military and phone company uses. The “3N” designation for the tetrode transistors represents the general approach of: “N” number + 1 = the actual number of leads, so 3N + 1 = 4; four leads on a tetrode. ( In a similar manner, note that 2N + 1 = 3; three leads on a standard triode transistor). |
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Copyright
© 2002 by Jack Ward http://www.transistormuseum.com |
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