1308 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 

 1.4 SUMMARY 



In paragraph 1.3, derivations were given or outlined for each of the 

 four small-signal short-circuit admittances associated with the hole flow, 

 electron flow, and barrier capacitances in junction transistors. The terms 

 appear in that order in the expressions which follow. 



yee=U^^^coth {s,Wo/L,) + qu.Dr^Sne/ lJ^ e'"" ^'""^ 



(29) 



-{-uaC 



Te 



dVc Lp sinh (spWo/Lp) Lp (31) 



" \dVcLp 



Sp QPnDp ^/qV^olkT 



csch (wo/Lp) -f coth (wo/Lp)] 



tanh (spWo/Lp) Lp 

 csch (wo/Lp) + coth (wo/Lp)] + ic^Cr) (l + ^-^-^f A 



/ \ (TpctOiMo / 



(32) 



in which all symbols are defined in Section 1.5. It should be noted that 

 collector multiplication operates on the current to the barrier capacitance 

 since the latter current is a hole current in the collector body. 



The term dw/dVc is the same for both p-n-p and n-p-n structures. 

 It is: for step junctions 



and for graded junctions 



Vc in equations (33) and (34) means dc electrostatic potential dif- 

 ference across the collector barrier. 



Equations (29) through (32) may be manipulated into many forms. 

 One of these sets which may be employed as a starting point for the 

 approximate forms given in the body of this chapter is: 



_ q [r Sp tanh (wp/Lp) , 1 , . ^ (on^ 



