DESIGN THEORY OF JUNCTION TRANSISTORS 1293 



at 25°C ao* <^ [l + ^ ^1 = 1 + 0.0003 ^ 1.0003 



L ^ O-ncJ 



70°C a* c- 1.03 



25°C ace = 7o^oq:o* = 0.992 X 0.993 X 1.0003 = 0.985 



7,0°C ace = 1.015 



9cc = -- Tr^ ^c cosh {w/LJ 



w V cO 



kT c)w 

 ^ — ^T/ S'- = 0.026 X 1.6 X 10""' X 0.039 

 qw dVc 



= 4.5 jumhos 



The parameters which determine frequency response are 



27r Tri/;^ 7r(3.6 X 10 ^r 

 Ct ^^ 2400 imfd/cvci for collector 

 Cr c^ 6500 iiufd/cTCi for emitter 



so that 



Cr^ = 6 iiiijd 



Ct, = 16 MM/d 



t The electron storage capacitances of the emitter and collector diffusion 

 admittances of this n-p-n transistor are : 



C.'=rr' = , .^^.?T9 Vina = 1690*.M/d 

 1.5aja 1.5 X 2.45 X 2t X 10^ 



Csc = T^ = 0.2 nnfd 



It is obvious that diffusion effects are most important at the emitter, 

 while depletion layer capacitance is important at the collector. 



The ohmic base spreading resistance of this unit is given (probably 

 within a factor of two) by 



rl^^ = ^^ ^-^^^^ = 278 ohms 

 * w 3.6 X 10-3 



