Lect. 11: BJT Circuits at DC

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Lect. 11: BJT Circuits at DC
β=100, v
BE,ON=0.7V, VCE,sat
=0.3V.
Desi
g
n the circuit so that I
C
=2mA and V
C
=5V in the active re
g
ion.
g
C
C
g
(1)What is R
c?
10 V
(1)5k
R
Ω
(2) What is I
E?
(3) What is V
E?
(1)

5

k
2 mA
C
R
=
=
Ω
2
(2) 22.02 mA
100
EBC
III=+=+=
(4) What is R
E?
(5)Iititii?
(3) 0.7
E
VV
=

(15)
(4) 7.08 k
202
E
E
V
R


=

(5)

I
s
it

i
n ac
ti
ve reg
i
on
?
2
.
02
,
(5) 5(0.7)5.7
CECEsat
VV
=
−−=>
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
Lect. 11: BJT Circuits at DC
V4V40.73.3 V
EBE
=
−=−=
1
V
?
V0
3.3
1 mA
3.3
E
E
E
I
R

===
Using VBE,ON=0.7V, β= 100,VCE,sat=0.2V
1
.
V
E =
?
2. I
E
= ?
100
~0.99
1101
CE
II
α
β
α
β
=
=
=
3. I
C= ?
4V
=?
1101
0.9910.99 mA
C
I
β
+
=×=
4
.
V
C
=?
5. I
B=?
V10100.994.7~5.3 V
CCC
IR=−=−×
1
I
1
~0.01 mA
1101
E
B
I
I
β
==
+
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
Lect. 11: BJT Circuits at DC
V6V60.75.3 V
EBE
=+−=−=
Usin
g
V
BEON
=0.7V
,

β
㴠㄰=
,
V
䍅獡s
㴰⸲=
V104.7107.522.48V
CC
I
=−
×
=−=
g
BE
,
ON
,
β
,

,
獡s
5.3
1.6 mA
3.3
E
I==
1.V
E = ?
V104.7107.522.48

V
CC
I
×
(not⁰潳獩扬=)
㴠=.㐸ⴵ.3㴠ⴲ.82
CE
V
2. V
C=?
3. I
B
=?
sat
V~VV5.30.25.5 V
CECE
+=+=+
105.5
0.96 mA
4.7
C
I
+−
==
1.60.960.64 mA
BEC
III=−=−=
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
Lect. 11: BJT Circuits at DC
1.V
E = ?
2. V
C=?
3. I
B, IC, IE=?
Transistor is cut-off!
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
High-Speed Circuits and Systems Laboratory
Electronic Circuits 1
Lect. 11: BJT Circuits at DC
VV0.7V
EEB
==
β=100
1.V
E = ?
VV0.7

V
EEB
VV
100.7
4.65 mA
2
E
E
I
R
+


===
2. I
C=?
2
E
R
0.994.654.6 mA
CE
II
α
=
=×=
3. V
C=?
4. I
B=?
VV
1046154V
CCC
IR

=+
=

+×=


104
.
615
.
4

V
=+×=
㐮㘵
〮〵A
1㄰1
E
B
I
I
β
===
+
β
,
V0.7(5.4)V
E
CECsat
=−−>
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
Lect. 11: BJT Circuits at DC
2
12
50
V15155 V
10050
(//)(100//50)333k
B
BB
BB
R
RR
RRR
=+==+
++
===Ω
β=100
1. I
E = ?
12
(//)(100//50)33
.
3

k
BBBB
RRR
===Ω
VV
BBBBBBEEE
I
RIR
I
=
+
2. V
C=?
1
E
B
I
I
β
=
+
VV
[(1)]
BBBE
E
I
RR
β

=
++
[(1)]
50.7
1.29 mA
3(33.3/101)
EBB
E
RR
I
β
++

==
+
128A
II
1.29
00128mA
I
1
.
28
m
A
V15151.2858.6 V
CE
CCC
II
IR
α
=
=
=+−=−×=
0
.
0128

mA
101
B
I
=
=
VV
071293457V
BBEEE
IR=+
=+×=
VV
45707387V
EBBE
V=−
=

=
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)

0
.
71
.
2934
.
57

V
=+×=
††
4
.
㔷0
.

.

=
V
==
Lect. 11: BJT Circuits at DC
2
Ignoring
B
I
111
V15
151.2858.6 V
CCC
IR
=
+−
=
−×=+
2
21
VVV8.60.79.3 V
ECEB
Q
=+=+=+
2
2
2
15V
159.3
2.85 mA
2
E
E
E
I
R
+−

===
285
I
E
=100
2
2
2
2
.
85
0.028 mA
1101
E
B
I
I
β
===
+
β
1. V
C,1=?
2. I
B2
=?
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
Lect. 11: BJT Circuits at DC
2
Considerin
g
,
B
I
DV
d?
112
Current in 1.280.0281.252 mA
CCB
RII
=
−=−=
D
oes
V
C1
go up or
d
own
?
1
V1551.2528.74 V
C
=
−×=
2
V8.740.79.44 V
E
=
+=
(Before, 8.6V)
2
E
2
159.44
2.78mA
2
E
I

==
β
=100
2,new
2.78
0.0275 mA
101
B
I==
(Before, 0.028mA)
β
ㄮ⁖
䌬C
㴿
㈮⁉

㴿
Prof. Woo-Young Choi
Electronic Circuits 1 (09/2)
B2