PRINCIPLES OF TRANSISTOR ACTION 243 



large part of holes; that is of carriers of opposite sign to those normally 

 in excess in the body of the semi-conductor. 



The collector is biased in the reverse, or negative direction. Current 

 flowing in the <2;ermanium toward the collector point j)rovides an electric 



Fig. 2 — Microphotograph of a cutaway model of a transistor 



field which is in such a direction as to attract the holes flowing from the 

 emitter. When the emitter and collector are placed in close proximity, a 

 large part of the hole current from the emitter will flow to the collector and 

 into the collector circuit. The nature of the collector contact is such as to 

 provide a high resistance barrier to the flow of electrons from the metal to 

 the semi-conductor, but there is little impediment to the flow of holes into 



