362 ni'J.I. SV.ST/':\f TECIIXICAL JOURXAL 



Our i)r()l)leni is to reex{)ress this relationship in tcrnis of the small a-c coni- 

 |)om'nts and show that it rcducos to the relationship 



'i'c — V.I = RMc + occit) (5.6) 



corresponding to the equivalent circuit. For small emitter current the 

 analysis is carried out conveniently as follows: The ratio of hole current to 

 the total current is —-^I./Ic. The ratio {Re + bR^/Rc corresponds to 

 Ga/G discussed in connection with Fig. 3. The ratio of hole current to total 

 current is given in (2.6) in terms of Ga/G and may be rewritten as 



_yh^ 1 - (gp/G) _ -8Ro . 



Ic \ + b {\ + b)Re' ^''•^^ 



giving 



bRc = Rc{\ + b)y Lh. (5.7) 



(Since Ic is negative and /« is positive this equation shows that bRc is nega- 

 tive, i.e., the conductivity has been increased by the hole current.) Putting 

 this value of Re + bRc into the equation for T^ — V j gives 



]'. - Vj = (Re + bRc)Ic 



= RcUc+ (1 + b)yll .(5.8) 



If we consider small a-c variations in the currents and voltages, this reduces 

 to the equation given by the equivalent circuit with 



«.-(! + bh. (5.9) 



The data of Section 2 indicate that for holes injected into ;z-type germanium 

 7 = 1, and since b — 1.5 we obtain ae = 2.5. 



The quantity Vj can be eliminated by using Vj = Rbii^ + ie) in equation 

 (5.3) for Ve and the small signal form of (5.8) for zv leading to the pair of 

 equations 



lu = {Re + Rb)i. + Rbic (5.10) 



Vc = {Rb + aeRe)ie + {Re + Rb)ic . (5.11) 



These equations are formally identical with those for the equivalent circuits 

 of the type-A transistor. 



It should be emphasized that although hole injection into //-type germa- 

 nium plays a role in both the type-A and the particular form of filamentary 

 transistor shown in Fig. 9, there are differences in the principles of operation. 

 One imj)ortant feature of the type-A is the high impedance of the rectifying 

 collector contact which, however, does not impede hole liow and another 

 important feature is the current amplification occurring at the collector 

 contact. Neither of these features is present in the filamentary type shown. 

 Instead, the high impedance at the collector terminal arises from the small 



