Page 220 - 30105-2003 การวิเคราะห์วงจรอิเล็กทรอนิกส์ความถี่สูง

212
5.

R
R
V CC TH V CC TH
ก ก (2.28) R = , R = ;
B 1 B 2
V V − V )
TH ( CC TH

) 5.7 $ &( R , R , R !
R . ก I = 5 mA !
$ " $- &( /
B 1 B 2 E C C
* + V CE = 0.5V CC ,V RC = 0.35V CC ,V RE = 0.15V CC ;
×
V = 0.5 12 = 6 V
CE
×
V = 0.35 12 = 4.2 V
RC
=
×
V RE = 0.15 12 1.8 V
×
I C 5 10 − 3
I = β F = 100 = 50 µA
B
0.35V 4.2
ก ก (2.24) R = CC = = 840 Ω
C
×
I C 5 10 − 3
×
0.15V 0.15 12
ก ก (2.25) R = CC = = 356.435 Ω
E
( β + ) 1 I B 50 10 − 6 (100 1+ )
×
F
×
=
ก ก (2.26) R TH = 15R = 15 356.435 5.346 kΩ
E
ก ก (2.27) V TH = I R +V BE + ( β F + ) 1 I R
B TH
B E
)
×
×
×
×
V = ( 50 10 − 6 × 5.346 10 3 ) + 0.6 + ( 101 50 10 − 6 × 356.435
TH
V TH = 2.667 V
V CC TH
R
ก ก (2.28) R B 1 =
V TH
R
V CC TH
R B 2 =
(V CC − V TH )
×
×
12 5.346 10 3
R B 1 = = 24.053 kΩ
2.667
×
×
12 5.346 10 3
R = = 6.873 kΩ
B 2
(12 2.667− )
$
$- &( /
R = 840 Ω $- &( / R = 820 Ω
C C
R E = 356.435 Ω $- &( / R E = 360 Ω

R B 1 = 24.053 kΩ $- &( / R B 1 = 24 kΩ
R = 6.873 kΩ $- &( / R = 6.8 kΩ
B 2 B 2
Ω
Ω
Ω
R = == = 820 , R = =Ω Ω = = 360 , R = = = = 24 k , R = = = = 6.8 k ;
Ω Ω Ω
Ω Ω
Ω Ω Ω
Ω Ω Ω
C E B 1 B 2
ก

ก
ก