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THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



sponds to a region in which resistance is very high. The points B and C 

 are particularly important for they represent points of inflection where 

 the resistance undergoes rapid change and the material is departing 

 most markedly from Ohm's Law. Ideally they should be sharp but in 

 practice there is usually considerable curvature. Though either inflection 

 point could presumably be used in detection processes, the point to the 

 right of the origin is for practical reasons, usually preferred. Point B 

 defines a voltage Eb at which substantial backward currents flow. It is 

 referred to simply as the reverse voltage. In a similar way, point C defines 

 a, forward voltage Ep- The distance between B and C {Eb + Ep) will be 

 referred to as the inflection interval. The difference in these quantities 

 {Eb — Ef) is also of interest. One-half of this voltage difference is re- 

 ferred to as the self-biasing voltage. It is a significant cjuantity readily 

 measured in practice by noting the d-c voltage across a large condenser 

 placed in series with the crystal and a supply of 60 cycles AC. For de- 

 tectors, point C should preferably be close to the origin and Ep should 



LOG I 



Fig. 2 — Idealized characteristic curves. 



