DESIGN THEORY OF JUNCTION TRANSISTORS 1273 



ohmic resistance of the base region were discussed briefly. Still more 

 recently, the dependence of base thickness on collector voltage was used 

 to explain output and feedback effects*. The present paper is both a 

 consolidation and an extension of the earlier works and borrows freely 

 from them. The diffusion current analysis of Appendix A is patterned 

 after Shockley's. 



1 4 Scope 



The design theory developed here is not complete, even for small 

 signal ac transmission. In particular, effects of large carrier emission 

 densities are not considered, nor are the effects of non-parallel junction 

 arrangements. Despite these omissions, it is hoped that the theory 

 developed will be both useful and instructive to those engineers charged 

 with transistor device and transistor circuit design. 



2.0 METHODS AND ASSUMPTIONS 



2.1 General 



In developing the design theory, it is convenient to break the transistor 

 down into several internal electronic functions and to consider their 

 dependence on structure and materials individually. These functions 

 are then fitted together and used to predict the terminal electrical char- 

 acteristics. With this approach, it seems proper to describe separately 

 the methods and assumptions used in analyzing each of the functions, 



2.2 List of Symbols 



The symbols listed here are used in the body of the paper. A separate 

 list for Appendix A appears at the end of that section. 



Emitter and collector currents are assumed to flow inward at the 

 corresponding terminals, in accord with the convention usually used for 

 transistors. 



a = gradient of (Nd-Na), usually given in atoms/cm . 



ace = short-circuit forward current transfer constant for theoretical 

 one-dimensional transistor. 



Cc = collector to base capacitance with emitter open-circuit ac. 



Cse, Csc = hole storage or diffusion capacitances at emitter and col- 

 lector. These capacitances are directly related to the current trans- 



* J M Early, Effect of Space-Charge Layer Widening in Junction Transistors, 

 I.R.E., Proc, 40, pp. 1401-1406, Nov., 1952. 



