DESIGN THEORY OF JUNCTION TRANSISTORS 1275 



Pi = hole concentration which would exist in the semi-conductor at 

 thermal equilibrium if donor and acceptor concentrations were zero. 

 Pn = thermal equilibrium concentration of holes in n-region. 

 q = electronic charge, 1.6 X 10~^^ coulombs. 

 q/kT = see kT/q. 



Tb, ni, rm = ohmic spreading resistances of base region, specifically, 

 the effective base to emitter feedback resistances for diffusion cur- 

 rents and for collector capacitance currents. 



n , r2 , n = geometrical radii in transistor of Fig. 2(b). 



T = temperature in °K. 



Vc = average or dc collector to base voltage. 



VJ = electrostatic potential across collector depletion region. 



Vs = electrostatic potential across emitter depletion layer at therma 

 equilibrium (no biases applied). 



Vc = small signal ac collector to base voltage. 



w, Wo = base region thickness. 



Wi , W2 , Wz = base region thicknesses in transistor of Fig. 2(b). 



Xm = thickness of collector depletion region. 



yce , Vce , Vec , Vcc = theorctlcal short circuit input, forward transfer, feed- 

 back, and output admittances for one-dimensional transistor. 



a, oiQ = short-circuit emitter to collector current transfer ratio and its 

 low-frequency value. 



a*, oo* = collector junction current multipUcation ratio and its low- 

 frequency value. 



j3, /So = current transport ratio across base region and its low-frequency 

 value. 



7, To = current emission ratio at emitter and its low-frequency value. 



€o = dielectric constant of vacuum, 8.854 X 10" farad/cm. 



A' = relative dielectric constant, e/eo . 



P, Pb = resistivity, base region resistivity. 



(^nc, (Tpc = conductivities produced by electrons and holes in collector 

 region. 



r, Tn , Tp = lifetimes of minority carriers. 



