1274 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



mission cutoff frequency and may be used as an alternative charac- 

 terization of that quantity. 



Cre , Ctc = theoretical depletion layer capacitances of emitter and col- 

 lector. 



D, DpjDn = diffusion constants for minority carriers, usually given in 

 cm /sec. 



/„ = D/tWo^ = current transmission or alpha cutoff frequency. 



Qee , Qce , Qec , Occ = low-frequeucy conductance components of ?/'s given 

 below. 



h^s = set of two terminal-pair parameters, defined by Guillemin, Com- 

 munication Networks, 2, p. 137, John Wiley and Sons. 



hn = short circuit input impedance. 



h2i = short circuit forward current transfer ratio. 



hu = open circuit feedback voltage ratio. 



hzz = open circuit output admittance. 



h = average or dc base current. 



Ipe , Inc , I PC , Inc = holc aud electrou components of average or dc emitter 

 and collector currents. 



Ipeo = emitter reverse current when collector is also reverse biased. 



Je = emitter current density in amperes/cm^. 



k = Boltzmann's constant. 



kT/q = average thermal energy per carrier, approximately 0.026 elec- 

 tron-volts at 25°C. 



L, Lpy Ln = diffusion length or average distance a minority carrier will 

 diffuse before recombining; average distance diffused in one life- 

 time (t). 



Naj Nd = concentration of acceptor and donor atoms in semi-con- 

 ductor, usually in atoms/cm^. 



n = concentration of electrons/cm^. 



Ui = electron concentration which would exist in the semi-conductor 

 at thermal equilibrium if donor and acceptor concentrations were 

 zero. 



Up = thermal equiUbrium concentration of electrons in p-region. 



p = hole concentration/cm'. 



