1296 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



The effective hole storage capacitances of the emitter and collector are: 



Cse = 3840 nnjd 

 Csc = 0.8 finfd 

 By the equations given in Section 3.0 



Tbi = 55 ohms 

 rb2 = 35 ohms 

 The low frequency values of the ''/i" parameters are 

 /i2i o^ -0.988 

 hu ^ 2.09 X 10"' 

 /i22 ^^ 0.17 fimho 

 hn ^ 26 + (0.012)55 o^ 26.7 



These theoretical values are compared with observed values in Table I. 

 The major discrepancy in /121 is charged to surface recombination of in- 

 jected holes, which was ignored in the calculation. It should be noted 

 that /i22 becomes 0.45 X 10~^ mho if the calculated value is corrected 

 by the ratio 0.032/. 012, which is the ratio of the measured and calcu- 

 lated (1 — a)'s or (1 -f /i2i)'s. The difference between computed and 

 measured hn is the sum of a number of effects. First, the actual (1 — a) 

 is greater than the computed value. Next, the junction temperature was 

 probably greater than the assumed 25°C. Finally, the carrier injection 

 level is high enough to modify the emitter diode properties in this 

 direction. 



The difference between calculated and observed current transmission 

 cutoff is greater than appears from the data, since the theoretical three 

 db response frequency is about 22 per cent higher than the "alpha 



Table 1 



