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Semiconductor Physics and Devices: Basic Principles, 4
th
 edition Chapter 12 
By D. A. Neamen Problem Solutions 
______________________________________________________________________________________ 
 From the definition of currents, we have 
 CE II  for the case of 0BI . Then 
 CF
t
BC
CSRFC I
V
V
II  
















 1exp 
 
















 1exp
t
BC
CS
V
V
I 
 When a C-E voltage is applied, then the B-C 
 becomes reverse biased, so 0exp 







t
BC
V
V
. 
 Then 
 CSCFCSRFC IIII   
 Finally, we find 
 
 
F
RFCS
CEOC
I
II





1
1
 
_______________________________________ 
 
12.53 
(a) 
















 1exp
t
BE
ESFC
V
V
II  
 
















 1exp
t
BC
CS
V
V
I 
 For 2.0BEV V, 
    











  1
0259.0
20.0
exp105992.0 14
CI 
   











  1
0259.0
exp10 13 BCV
 
 
10101197.1  
   











  1
0259.0
exp10 13 BCV
 
 For 5.0 BCCB VV V 
 510 104214.2101197.1  CI 
 
510421.2  A 21.24 A 
 For 25.0 BCCB VV V 
 910 105561.1101197.1  CI 
 
91044.1  A 
 For 0 BCCB VV V 
 10101197.1 CI A 
(b) For 4.0BEV V, 
 7105277.2 CI 
   











  1
0259.0
exp10 13 BCV
 
 
 For 5.0 BCCB VV V 
 57 104214.2105277.2  CI 
 
510396.2  A 24 A 
 For 25.0 BCCB VV V 
 97 105561.1105277.2  CI 
 71051.2  A 251.0 A 
 For 0 BCCB VV V 
 7105277.2 CI A 2528.0 A 
(c) For 6.0BEV V, 
 4107063.5 CI 
   











  1
0259.0
exp10 13 BCV
 
 For 5.0 BCCB VV V 
 54 104214.2107063.5  CI 
 
410464.5  A 5464.0 mA 
 For 25.0 BCCB VV V 
 4107063.5 CI A 5706.0 mA 
_______________________________________ 
 
12.54 
  satVCE 
 
  









R
F
CFBF
BRC
t
II
II
V




1
1
ln 
 
  
     














150.0
975.0
5975.01975.0
15.015
ln0259.0
B
B
I
I
  
 
 







 5.6
125.0975.0
25.4
ln0259.0
B
B
I
I
 
 15.0BI A,   187.0satVCE V 
 25.0BI A,   143.0satVCE V 
 50.0BI A,   115.0satVCE V 
 0.1BI A,   0956.0satVCE V 
_______________________________________ 
 
12.55 
 (a) (i) 1036.0
25.0
0259.0

E
t
e
I
V
r k 
   121035.06.103  jeee Cr 
 
1110626.3  s 26.36 ps 
 (ii) 
 
 252
1065.0
2
242 

n
B
b
D
x
 
 
111045.8  s 5.84 ps