414 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1952 



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Fig. 1 — The type A transistor structure. 



rectifying properties as a result of the 'p-n barrier (indicated by the 

 dotted hnes) existing at the interface between the n-type bulk material 

 and small p-type inserts under each point. When the collector is biased 

 with a moderately large negative voltage (in the reverse direction) so 

 that the collector barrier has relatively high impedance, a small amount 

 of reverse current flows from the collector to the base in the form of 

 electrons as indicated by the small black circles. Now, if the emitter is 

 biased a few tenths of a volt positively in the forward direction, a cur- 

 rent of holes (indicated by the small open circles) is injected from the 



Fig. 2 — Schematic diagram of a point-contact transistor. 



