EARLY TRANSISTOR HISTORY AT TEXAS INSTRUMENTS  Bill Brower
Oral History – Bill Brower (Continued) A tetrode variation of the transistor was developed to increase the high frequency characteristics.  A second base wire was bonded on the opposite side of the bar, and by biasing this second base in a negative direction, the active base area could be reduced to gain higher frequency operation.   After more than 40 years my recollection of the frequency range of the triode transistors is rather sketchy.  They could operate of course in the AM broadcast band and possibly much higher. Considerable effort was directed at increasing the reliability of the transistors.  Moisture was the main problem, causing high reverse leakage and eventual failure.  Metal cans and headers for hermetic sealing was used for military transistors, although special epoxy plastics were used commercially.  The grown junction transistors were eventually discontinued when the epitaxial transistor process became available.  The grown junction process was labor intensive and not easily automated. But therein lies another story!! ______________	Oral History – Bill Brower (Continued) Here are some examples of the transistors discussed by Mr. Brower.  The 900 series was used by TI to introduce the grown junction silicon type.  The 901 was one of the first to be sold commercially.  There is no mistaking the outline of the state of Texas stamped on the back of the transistors! ______________
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