bjt - analysis of bias
TRANSCRIPT
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BJT – Analysis of Bias
Yong Heui Cho @ Mokwon University
Some of slides are referred to:[1] A. S. Sedra & K. C. Smith, Microelectronic Circuits.
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Electronic Circuits
8. BJT – Operational Principle
9. BJT – Model
10. BJT – Analysis of Bias
11. Analysis of CE Amplifier
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CE Amplifier• CE (Common Emitter)• Input: Base, Output: Collector• Common: Emitter
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CB Amplifier• CB (Common Base)• Input: Emitter, Output: Collector• Common: Base
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CC Amplifier• CC (Common Collector)• Emitter Follower• Input: Base, Output: Emitter• Common: Collector
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ComparisonType CE CB CCinput Base Emitter Base
output Collector Collector Emittercommon Emitter Base CollectorV gain large large noneI gain large none large
application first stage amplifier
high fre-quency am-
plifierbuffer
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Bias Point• Quiescent point• Active mode
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CE Amplifier• 4 R and 1 TR
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Active Condition• Collector Current (IC) = about mA• CE Voltage (VCE) = VCC/2
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Analysis of Bias (I)• Thevenin equivalent circuit
CCBB
BBB V
RRRV
21
2
21
2111 //
BB
BBBBB RR
RRRRR
VBB
RB
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Analysis of Bias (II)• B-E loop: collector current (IC)
VBB
RB
VCC
RC
RE
BEBBE
EEBEBBBB
IRRVRIVRIV
)1(
BCBE IIII )1(
EB
BEBBB RR
VVI)1(
E
BEBB
EB
BEBBC
RVV
RRVVI
)1()(
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Analysis of Bias (III)• C-E loop: CE voltage (VCE)
VBB
RB
VCC
RC
RE
BCBE IIII )1(
EECECCCC RIVRIV
)( ECCCC
EECCCCCE
RRIVRIRIVV
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Selection of R
kRR BB 10, 21
BE RR
LC RR