BJT Topologies – AC Characteristics · PDF fileZ CB : low CE : high CC : high in ... BJT...
Transcript of BJT Topologies – AC Characteristics · PDF fileZ CB : low CE : high CC : high in ... BJT...
Young Won Lim08/04/2017
BJT Topologies – AC Characteristics
Young Won Lim08/04/2017
Copyright (c) 2012 – 2017 Young W. Lim.
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BJT Topologies – AC Characteristics 3 Young Won Lim
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Input Characteristic CurvesOutput Characteristic Curves
BJT Topologies – AC Characteristics 4 Young Won Lim
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CE Amplifier : Linear Region
E
B
Cn
p
n
+
+
– –
V BE V CE
n
p
n
V CBC
B
E
Common Emitter
Active region
V BE V CE
V CB
V BBV RB
V RC V CC
Input Characteristics Output Characteristics
0.7V
BJT Topologies – DC Characteristics 5 Young Won Lim
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CE Amplifier : Saturation Region
E
B
Cn
p
n
Common Emitter
V BBV RB
V RC V CCsaturation
+
+
– –
V BE V CE
n
p
n
V BC
C
B
E
+
–
V BE V CE
V BC
0.7V
BJT Topologies – AC Characteristics 6 Young Won Lim
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CC Amplifier : Characteristic Curves
Input Characteristics Output Characteristics
Common Collector 3
Active region
E
B
C n
p
n
+
+
– –
V BE V CE
n
p
n
V CBC
B
E
V BC V EC
V BC
V BE−V CE
V EC
−V CE
BJT Topologies – AC Characteristics 7 Young Won Lim
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CB Amplifier : Characteristic Curves
Input Characteristics Output Characteristics
Active region
Common Base
n p n
B
E C
+
+
– –
V BE V CE
n
p
n
V CBC
B
E
V EB V EB
IE
V CB
IC
V CE−V BE
BJT Topologies – AC Characteristics 8 Young Won Lim
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Vin & V
out Phase Relationship
BJT Topologies – AC Characteristics 9 Young Won Lim
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Notations
V CE
vce = vce(t)
ac instantaneous
V ce
ac rmsac avgac p-to-p
DC AC DC + AC
V CE + v ce
UPUPlowlow
UPlow
BJT Topologies – AC Characteristics 10 Young Won Lim
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CE Amplifier : Phase Relationship
E
B
Cn
p
n
Common Emitter
vs( t) vs( t)
vs
V BB
V BB
vs + V BB
Input Characteristics
V BB V BB
+V s
V BB
−V s
inc IB+ I b → inc IC+ I c , I E+ I e
dec IB− I b → dec IC−I c , IE− I e
BJT Topologies – AC Characteristics 11 Young Won Lim
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CE Amplifier : Phase Relationship
E
B
Cn
p
n
Common Emitter Input Characteristics Output Characteristics
increasing vi direction
decreasing vo direction
Active region
BJT Topologies – AC Characteristics 12 Young Won Lim
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CC Amplifier : Phase Relationship
Input Characteristics Output CharacteristicsCommon Collector 3
Active region
E
B
C n
p
n
V BC
V BE−V CE
V EC
−V CE
increasing vi direction
increasing vo direction
BJT Topologies – AC Characteristics 13 Young Won Lim
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CB Amplifier : Phase Relationship
Input Characteristics Output Characteristics
Active region
Common Base
n p n
B
E C
V EB
IE
V CB
IC
V CE−V BE
increasing vi direction
increasing vo direction
BJT Topologies – AC Characteristics 14 Young Won Lim
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DC bias only circuitsDC + small AC AC only circuits
BJT Topologies – AC Characteristics 15 Young Won Lim
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BJT Amplifier Configurations
n p nE
B
C
Common Base
n p n
B
Common Base
E
B
C
Common Emitter
n
p
n
E
BC
Common Emitter
n
p
n
E
B
C
Common Collector
n
p
n
E
B
C
Common Collector
n
p
n
E C
BJT Topologies – AC Characteristics 16 Young Won Lim
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Basic BJT Configuration Circuits
B
Common Base
E
BC
Common Emitter
E
B
C
Common Collector
E C
BE
BC E
B
C
E C−V EE −V CC
V CC
V BB −V BB
−V CC
BJT Topologies – AC Characteristics 17 Young Won Lim
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DC Bias
B
Common Base
E
BC
Common Emitter
E
B
C
Common Collector
E C
BJT Topologies – AC Characteristics 18 Young Won Lim
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DC Bias + AC Small Signal
B
Common Base
E
BC
Common Emitter
E
B
C
Common Collector
E C
BJT Topologies – AC Characteristics 19 Young Won Lim
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AC Equivalent Circuits
B
Common Base
E
BC
Common Emitter
E
B
C
Common Collector
E C
B
E C
vo
E
B
C
vo
E
BC
vo
BJT Topologies – AC Characteristics 20 Young Won Lim
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CB Amplifiers – DC Bias, AC Signal, Output LoadCE Amplifiers – DC Bias, AC Signal, Output LoadCC Amplifiers – DC Bias, AC Signal, Output Load
BJT Topologies – AC Characteristics 21 Young Won Lim
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Common Base
B
E C
B
E C
B
E C
DC Bias DC Bias + AC Signal
AC Signal AC Signal + Load
B
E C
DC Bias + AC Signal + Load
B
E C
vo
vo
vo
BJT Topologies – AC Characteristics 22 Young Won Lim
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Common Emitter
E
BC
E
BC
E
BC
E
BC
E
BC
DC Bias DC Bias + AC Signal DC Bias + AC Signal + Load
AC Signal AC Signal + Load
vo
vo
vo
BJT Topologies – AC Characteristics 23 Young Won Lim
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Common Collector
E
B
C
E
B
C
E
B
C
E
B
C
E
B
C
DC Bias DC Bias + AC Signal DC Bias + AC Signal + Load
AC Signal AC Signal + Load
vo
vo
vo
BJT Topologies – AC Characteristics 24 Young Won Lim
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AC Equivalent ModelT-modelPi-model
Input ImpedanceOutput Impedance Voltage Gain Current Gain
BJT Topologies – AC Characteristics 25 Young Won Lim
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AC t & pi models
B
Common Base
E
B
C
Common Emitter
E
B
C
Common Collector
E C
B
Common Base
E
B
C
Common Emitter
E
B
C
Common Collector
E C
BJT Topologies – AC Characteristics 26 Young Won Lim
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Input Impedance Zin
Zin : low
Ie
: Large
Zin
: high
Ib
: Small
Zin
: high
Ib : Small
E
B
C
Common Base
E
B
C
Common Emitter
E
B
C
Common Collector
re ' β re ' β(re '+RE)
I e Ib Ib
BJT Topologies – AC Characteristics 27 Young Won Lim
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Output Impedance Zin
Zout
: high
Thevenin R
Zout
: high
Thevenin R
Zout
: low
Thevenin R
E
B
C
Common Base
E
B
C
Common Emitter
E
B
C
Common Collector
RC RC re '
BJT Topologies – AC Characteristics 28 Young Won Lim
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Voltage Gain Av
Common Base Common Emitter Common Collector
Av : high A
v : high A
v: unityRC /re ' RC /re ' 1
I e I c I e
I c
I e
I e
BJT Topologies – AC Characteristics 29 Young Won Lim
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Current Gain Ai
Common Base Common Emitter Common Collector
I e I c
I c
IbIb
I c
Ai : unity A
i: high A
i: high1 β β
BJT Topologies – AC Characteristics 30 Young Won Lim
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BJT Configuration Properties
BJT Topologies – AC Characteristics 31 Young Won Lim
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BJT Configuration Properties (1)
input Z : lowoutput Z : highvoltage gain : highcurrent gain : unity
input Z : highoutput Z : highvoltage gain : highcurrent gain : high
input Z : highoutput Z : lowvoltage gain : unitycurrent gain : high
BCCB CE EC
BEEB
n p nE
B
C
Common Base
E
B
C
Common Emitter
n
p
n
E
B
C
Common Collector
n
p
n
RF Applications Widely used Emitter FollowerBuffer to Low Impedance Load
Low Zin
Low Zout
BJT Topologies – AC Characteristics 32 Young Won Lim
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BJT Configuration Properties (2)
Zin : low
Zout
: high
Av : high
Ai : unity
Zin
: high
Zout
: high
Av
: high
Ai
: high
Zin
: high
Zout
: low
Av
: unity
Ai
: high
n p nE
B
C
Common Base
E
B
C
Common Emitter
n
p
n
E
B
C
Common Collector
n
p
n
re '
RC
RC /re '
1
β re '
RC
RC /re '
β
β(re '+RE)
re '
1
β
BJT Topologies – AC Characteristics 33 Young Won Lim
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BJT Configuration Properties
re '
RC
β re '
RC
β
β(re '+RE)
re '
1
CB : low CE : high CC : highZin
CC : lowZout CE : high CB : high
CC : unity CB : highCE : high RC /re ' RC /re '
CB : unity CE : high CC : high
Av
Ai 1 β
CB : low
CB : high
CB : high
CB : unity
CE : high
CE : high
CE : high
CE : high
CC : high
CC : low
CC : unity
CC : high
re '
RC
RC /re '
1
β re '
RC
RC /re '
β
β(re '+r E)
re '
1
β
Zin
Zout
Av
Ai
Common Base Common Emitter Common Collector
BJT Topologies – AC Characteristics 34 Young Won Lim
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BJT Configuration Properties
CB : low
CB : high
CB : high
CB : unity
CE : high
CE : high
CE : high
CE : high
CC : high
CC : low
CC : unity
CC : high
re '
RC
RC /re '
1
β re '
RC
RC /re '
β
β(re '+r E)
re '
1
β
Zin
Zout
Av
Ai
Common Base Common Emitter Common Collector
CB : low
CB : high
CB : high
CB : unity
CE : med
CE : med
CE : med
CE : med
CC : high
CC : low
CC : unity
CC : high
r e
RC
α RC
(R s+r e)
α
r π=(β+1)r e
RC ∣∣ r o
β(RC ∣∣ r0)
(R s+rπ)
β ro
(R c+r o)
(β+1)[re+(ro∣∣RL)]
r o ∣∣[re+R s
(β+1) ]
(b+1)(RL ∣∣r o)
R s+(β+1)[ re+(RL∣∣r o)]
(β+1)r o
r o+RL
Zin
Zout
Av
Ai
Common Base Common Emitter Common Collector
ro , Rs , RE are used
BJT Topologies – AC Characteristics 35 Young Won Lim
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BJT Configuration Properties
CB : low
CB : high
CB : high
CB : unity
CE : high
CE : high
CE : high
CE : high
CC : high
CC : low
CC : unity
CC : high
re '
RC
RC /re '
1
β re '
RC
RC /re '
β
β(re '+r E)
re '
1
β
Zin
Zout
Av
Ai
Common Base Common Emitter Common Collector
CB : low
CB : high
CB : high
CB : unity
CE : med
CE : med
CE : med
CE : med
CC : high
CC : low
CC : unity
CC : high
r e∣∣ RE ≈ r e
RC
RC
r e, RC ∣∣ RL
r e
R1 ∣∣ R2 ∣∣β re
RC (r e+Rs
β )∣∣RE =Rs
β ∣∣RE
RE
(re+RE )≈ 1
Zin
Zout
Av
Ai
Common Base Common Emitter Common Collector
VDB
RC
r e, RC ∣∣ RL
r e
R1 ∣∣ R2 ∣∣β(r e+RE)
BJT Topologies – AC Characteristics 36 Young Won Lim
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AC Equivalent Circuits
Input Characteristic CurvesOutput Characteristic Curves
BJT Topologies – AC Characteristics 37 Young Won Lim
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Storing Magnetic Energy
v vR
vL
i iR
iL
= +
= =
Young Won Lim08/04/2017
References
[1] http://en.wikipedia.org/[2] J.H. McClellan, et al., Signal Processing First, Pearson Prentice Hall, 2003