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Young Won Lim06/28/2017
BJT Topologies – Characteristics
Young Won Lim06/28/2017
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BJT Topologies – Characteristics 3 Young Won Lim
06/28/2017
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 – Characteristics 4 Young Won Lim
06/28/2017
BJT Configuration Properties
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 – Characteristics 5 Young Won Lim
06/28/2017
BJT Configuration Properties
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 – Characteristics 6 Young Won Lim
06/28/2017
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 – Characteristics 7 Young Won Lim
06/28/2017
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 – Characteristics 8 Young Won Lim
06/28/2017
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 – Characteristics 9 Young Won Lim
06/28/2017
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 – Characteristics 10 Young Won Lim
06/28/2017
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 – Characteristics 11 Young Won Lim
06/28/2017
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 – Characteristics 12 Young Won Lim
06/28/2017
BJT Configuration Properties
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 – Characteristics 13 Young Won Lim
06/28/2017
BJT Topologies – Characteristics 14 Young Won Lim
06/28/2017
DC Bias
B
Common Base
E
BC
Common Emitter
E
B
C
Common Collector
E C
BJT Topologies – Characteristics 15 Young Won Lim
06/28/2017
DC Bias + AC Small Signal
B
Common Base
E
BC
Common Emitter
E
B
C
Common Collector
E C
BJT Topologies – Characteristics 16 Young Won Lim
06/28/2017
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 – Characteristics 17 Young Won Lim
06/28/2017
AC Equivalent Circuits
BJT Topologies – Characteristics 18 Young Won Lim
06/28/2017
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 – Characteristics 19 Young Won Lim
06/28/2017
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 – Characteristics 20 Young Won Lim
06/28/2017
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 – Characteristics 21 Young Won Lim
06/28/2017
AC Equivalent Circuits
BJT Topologies – Characteristics 22 Young Won Lim
06/28/2017
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 – Characteristics 23 Young Won Lim
06/28/2017
AC Equivalent Circuits
BJT Topologies – Characteristics 24 Young Won Lim
06/28/2017
Storing Magnetic Energy
v vR
vL
i iR
iL
= +
= =
Young Won Lim06/28/2017
References
[1] http://en.wikipedia.org/[2] J.H. McClellan, et al., Signal Processing First, Pearson Prentice Hall, 2003
