EARLY TRANSISTOR HISTORY AT

TEXAS INSTRUMENTS 

Elmer Wolff Jr

 

Oral History – Elmer Wolff Jr (Continued)

 

Mark really knew how to keep the project money flowing, even though the Semiconductor Operation wasn’t contributing any funds to TI at that early stage.  The market in the hearing aid business was not big enough to support the efforts necessary to achieve Mr. Haggerty’s dream of volume semiconductor manufacturing and industry usage. 

 

The power consumption of vacuum tubes relative to the transistor made the portable radio a natural target for volume transistor applications.  Our challenge was to develop devices with enough frequency capability to address the AM radio broadcast band.  At that time we never dreamed that anyone could ever get to the FM band, much less the TV band.

 

To obtain the necessary device frequency performance for radio applications with grown junction structures, it was necessary to produce very thin base layers in the grown crystal.  We did not have many options since the growth rate of the crystal could not be adjusted very easily.  The dopants for the base and for the emitter of the transistor were added to the liquid germanium within a fraction of a second of each other.  I can still vividly remember Boyd and I calling signals to each other on the timing of the dropping of the charges.  This was a two man operation, with one watching the crystal to insure that the charge did not bounce out of the crucible, and the other man releasing the charge. 

 

   

 

Oral History – Elmer Wolff Jr (Continued)

 

Many days, nights and weekends were spent in bringing the grown junction transistor performance to radio applications capability.  The first radio required six, seven or eight transistors to produce the desired sensitivity and sound.  These first radios were not economically feasible with that many expensive devices involved.  As the transistors improved, our applications team worked the required number down to five devices.  The real leap came by generating what Boyd and I called a grown diffused junction device.  As the name implies, the base layer was generated by adding the base dopant and emitter dopant to the germanium melt at the same time.  The temperature of the puller was raised and the crystal that had already been grown was melted back just a little – it was held at a “no growth” temperature for a predetermined time and then the crystal was finished in the normal manner.  The secret was that the “p-type” dopant material had a higher diffusion coefficient than the “n-type” dopant, and the resulting base layer diffused into the collector portion of the crystal.  This base layer was very thin and was controlled by the dwell time and dopant concentrations.  This process development permitted the RF amplifier and the Mixer to be combined into a single transistor and the four transistor radio was born.

 

 

 

Wolff Oral History, Page 6

 

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