1284 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



9E 



C9 — 



y^rVr 



Y.«V, 



Fig. 4 — Simplified equivalent circuits for "one-dimensional" transistor. 



or three db point f of the current transmission amplitude, appears in 

 the admittances in the form of storage capacitance or as transfer delay. 

 These result from minority carrier storage in the base region and are of 

 the same nature as hole storage capacitances in semi-conductor diodes. 

 If desired, further simplication can be obtained by eliminating the 

 effective power loss in the storage capacitances as shown in Fig. 4(b). 

 In this arrangement, as in the more rigorous forms preceding it, the 

 forward transfer admittance yce is a little smaller than the input admit- 

 tance yee and the feedback admittance yec is not quite as large as the 

 output admittance ycc • This makes the circuit delta {yeeVcc — yceyec) 

 greater than zero so that the structure is inherently stable when 7 

 and a* are unity. 



3.3 Depletion Layer Capacitances 



Even in the absence of applied potentials, there exists at useful p-n 

 junctions a depletion layer in which the density of mobile carriers is low, 



t R. L. Pritchard has pointed out that this three db point is 22 per cent larger 

 than coa as defined here. See R. L. Pritchard, Frequency Variations of Current- 

 Amplification Factor for Junction Transistors, l^roc. I.R.IO,, 40, p. 1476, Nov., 

 1952. 



