Young Won Lim07/14/2017
BJT Topologies – Basic Bias
Young Won Lim07/14/2017
Copyright (c) 2012 – 2017 Young W. Lim.
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BJT Topologies – Basic Bias 3 Young Won Lim
07/14/2017
BJT Amplifier Topologies
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 – Basic Bias 4 Young Won Lim
07/14/2017
Common Base Topology
n p n
E
B
C
Current Flow
Common Base
n p n
E C
B
Current Flow
Common Base
IN OUT IN OUT
BJT Topologies – Basic Bias 5 Young Won Lim
07/14/2017
Common Emitter Topology
E
B
C
Current Flow
Common Emitter
n
p
n E
B
C
Current Flow
Common Emitter
n
p
n
IN
OUT
IN
OUT
BJT Topologies – Basic Bias 6 Young Won Lim
07/14/2017
Common Collector Topology
E
B
C
Current Flow
Common Collector
n
p
n
E
B
C
Current Flow
Common Collector
n
p
n
IN
OUT
IN
OUT
BJT Topologies – Basic Bias 7 Young Won Lim
07/14/2017
Forward bias (BE) & Reverse bias (CB)
E
B
C E
B
C
n
p
n
n
p
n
Common CollectorCommon EmitterCommon Base
n p n
E C
B
n
p
n
E
B
C
n
p
n
E
B
C
V BE
V CB
forward biasreverse bias
V BE
V CB
forward biasreverse bias
V BE
V CB
forward biasreverse bias
n p n
B
E C
BJT Topologies – Basic Bias 8 Young Won Lim
07/14/2017
Bias for the Active Region
+
–
+
–
+
–
BJT Topologies – Basic Bias 9 Young Won Lim
07/14/2017
B2B Diodes
Common CollectorCommon EmitterCommon Base
n p n
E C
B
n
p
n
E
B
C
n
p
n
E
B
C
V BE
V CB
forward bias
reverse bias
V BE
V CB
forward bias
reverse bias
V BE
V CB
forward bias
reverse bias
Active region Active region Active region
Active Region
BJT Topologies – Basic Bias 10 Young Won Lim
07/14/2017
Biasing B2B Diodes
Common CollectorCommon EmitterCommon Base
n p n
E C
B
n
p
n
E
B
C
n
p
n
E
B
C
V BE
V CB
forward bias
reverse bias
V BE
V CB
forward bias
reverse bias
V BE
V CB
forward bias
reverse bias
++ – –
+
+–
– +
+–
–
Active region Active region Active region
Active Region
BJT Topologies – Basic Bias 11 Young Won Lim
07/14/2017
+ +
Polarities of Two voltage supplies
E
B
C E
B
C
n
p
n
n
p
n
Common CollectorCommon EmitterCommon Base
V BE V CBV BE
V CBV BE
n p n
B
E C
Active Region
V CBE
B
C E
B
C
+
+
–
–
+
–
+
– +
–
–
+
–
–
V BE
V CB
forward bias
reverse bias
V BE
V CB
forward bias
reverse bias
V BE
V CB
forward bias
reverse bias
Active region Active region Active region
BJT Topologies – Basic Bias 12 Young Won Lim
07/14/2017
Two voltage supplies Bias
E
B
C E
B
C
n
p
n
n
p
n
Common CollectorCommon EmitterCommon Base
V BE
V CB
forward biasreverse bias
V BE
V CB
forward biasreverse bias
V BE
V CB
forward biasreverse bias
V BE V CB V BE V CE V CB V CE
n p n
B
E C
Active Region
Active region Active region Active region
BJT Topologies – Basic Bias 13 Young Won Lim
07/14/2017
Controlling VBE
& VCB
E
B
C E
B
C
n
p
n
n
p
n
Common CollectorCommon EmitterCommon Base
V BE
V CB
V BE
V CE
V CB
V CE
n p n
B
E C
Voltage of B from E
Voltage of C from B
Voltage of B from E
Voltage of C from E
Voltage of Cfrom B
Voltage of C from E
V CB + V BE V CB + V BE
+
–
–
+
–
+
–
+
–
+
–
+
Active Region
Direct Control Indirect Control Indirect Control
BJT Topologies – Basic Bias 14 Young Won Lim
07/14/2017
Slope Controlling Resistors Active Region
Input Characteristics Output Characteristics
BJT Topologies – Basic Bias 15 Young Won Lim
07/14/2017
Two Voltage Sources
n p n
B E
B
C E
B
C
n
p
n
n
p
n
++
+
+
+
+
– –
–
–
– – V BE V CB
V BE V CE V CB V CE
n p n
n
p
n
n
p
n
E C
V CB V BE
E B C
C
B
E
E
B
C
Common CollectorCommon EmitterCommon Base
Active Region
Active region Active region Active region
BJT Topologies – Basic Bias 16 Young Won Lim
07/14/2017
CE & CC Comparison
E
B
C E
B
C
n
p
n
n
p
n
+
+
+
+
– –
–
–
V BE V CE V CB V CE
n
p
n
n
p
n
V CB V BEC
B
E
E
B
C
Common Collector 2Common Emitter
E
B
C
n
p
n
++
–
–
V CB V CE
n
p
n
V BEE
B
C
Common Collector
Active Region
Active region Active region Active region
BJT Topologies – Basic Bias 17 Young Won Lim
07/14/2017
Bias for the Saturation Region
+
–
+
–
+
–
BJT Topologies – Basic Bias 18 Young Won Lim
07/14/2017
Large IC & Small V
CE
Input Characteristics Output Characteristicsac
tive
satu
rati
on
Large VBB
Large Ic
Large Voltage Drop across R
Small VCE
Saturated Current I
C
Saturation Region
BJT Topologies – Basic Bias 19 Young Won Lim
07/14/2017
B2B Diodes
Common CollectorCommon EmitterCommon Base
n p n
E C
B
n
p
n
E
B
C
n
p
n
E
B
C
V BE
V BC
forward bias V BE
V BC
forward bias V BE
V BC
forward bias
++ – –
++
–
– ++
–
–
forward bias forward bias forward bias
saturation saturation saturation
V BE V BC
V BE
V BC V BE
V BC
Saturation Region
BJT Topologies – Basic Bias 20 Young Won Lim
07/14/2017
Voltage Supply Polarities
E
B
C E
B
C
n
p
n
n
p
n
Common CollectorCommon EmitterCommon Base
V BE forward bias V BE forward bias V BE forward bias
n p n
B
E C
V BC V BC V BCforward bias forward bias forward bias
saturation saturation saturation
+
+
++
–
–
– –
+
–
+
–
Saturation Region
+
–
+– V BE V BC
V BE
V BCV BE
V BC
E
B
CE
B
C
smal
lV
CE
small
VCE
BJT Topologies – Basic Bias 21 Young Won Lim
07/14/2017
Two Voltage Sources
n p n
B E
B
C E
B
C
n
p
n
n
p
n
++
+
+
++
–
–
– –
– –
V BE V BC
V BE V CE V BC V CE
n p n
n
p
n
n
p
n
E C
V BC V BE
E B C
C
B
E
E
B
C
Common CollectorCommon EmitterCommon Base
saturation saturation saturation
+
–
+
–
Saturation Region
BJT Topologies – Basic Bias 22 Young Won Lim
07/14/2017
CE & CC Comparison
E
B
C E
B
C
n
p
n
n
p
n
Common CollectorCommon Emitter
saturation saturation
E
B
C
n
p
n
Common Collector 2
saturation
Saturation Region
+
+
++
–
–
– –
V BE V CE V BC V CE
n
p
n
n
p
n
V BC V BE
C
B
E
E
B
C
+
–
+
– +
+
–
–
V BC V CE
n
p
n
V BE
E
B
C
+
–
BJT Topologies – Basic Bias 23 Young Won Lim
07/14/2017
BJT Topologies – Basic Bias 24 Young Won Lim
07/14/2017
Active and Saturation Regions (1)
Common CollectorCommon EmitterCommon Base
saturation saturation saturation
active active active
Large VBB
, Small VCE
Large VBB
, Small VCE
Large VBB
, Small VCE
n p n
B E
B
C E
B
C
n
p
n
n
p
n
E C
n p n
B E
B
C E
B
C
n
p
n
n
p
n
E C
BJT Topologies – Basic Bias 25 Young Won Lim
07/14/2017
Active and Saturation Regions (2)
Common CollectorCommon EmitterCommon Base
saturation saturation saturation
++
+
+
+
+
– –
–
–
– – V BE V CB
V BE V CE V CB V CE
n p n
n
p
n
n
p
n
V CB V BE
E B C
C
B
E
E
B
C
active active active
++
+
+
++
–
–
– –
– –
V BE V BC
V BE V CE V BC V CE
n p n
n
p
n
n
p
n
V BC V BE
E B C
C
B
E
E
B
C
+
–
+
–
BJT Topologies – Basic Bias 26 Young Won Lim
07/14/2017
Active and Saturation Regions (3)
Common CollectorCommon Emitter
saturation saturation saturation
active active
Common Collector 2
E
B
C E
B
C
n
p
n
n
p
n
E
B
C
n
p
n
E
B
C E
B
C
n
p
n
n
p
n
E
B
C
n
p
n
active
BJT Topologies – Basic Bias 27 Young Won Lim
07/14/2017
Active and Saturation Regions (4)
Common CollectorCommon Emitter
saturation saturation
active active
saturation
active
Common Collector 2
+
+
++
–
–
– –
V BE V CE V BC V CE
n
p
n
n
p
n
V BC V BE
C
B
E
E
B
C
+
–
+
– +
+
–
–
V BC V CE
n
p
n
V BE
E
B
C
+
–
+
+
+
+
– –
–
–
V BE V CE V CB V CE
n
p
n
n
p
n
V CB V BEC
B
E
E
B
C ++
–
–
V CB V CE
n
p
n
V BEE
B
C
BJT Topologies – Basic Bias 28 Young Won Lim
07/14/2017
BJT Topologies – Basic Bias 29 Young Won Lim
07/14/2017
Common Base (1)
n p n
E
B
C
Common Base
n p n
E
B
C
Electron Flow Current Flow
Common Base
forward bias reverse bias forward bias reverse bias
BJT Topologies – Basic Bias 30 Young Won Lim
07/14/2017
Common Base (2)
n p n
E
B
C
Electron Flow
n p n
E C
n p n n p n
B
E
B
C E C
B
Current Flow
Common Base Common Base
BJT Topologies – Basic Bias 31 Young Won Lim
07/14/2017
Common Emitter (1)
E
B
C
E
B
C
Electron Flow Current Flow
Common Emitter Common Emitter
n
p
n
n
p
nforward bias
reverse bias
forward bias
reverse bias
BJT Topologies – Basic Bias 32 Young Won Lim
07/14/2017
Common Emitter (2)
E
B
C
E
B
C
Electron Flow Current Flow
Common Emitter Common Emitter
n
p
n
n
p
n
n
p
n
n
p
n
BJT Topologies – Basic Bias 33 Young Won Lim
07/14/2017
Common Collector (1)
E
B
C
E
B
C
Electron Flow Current Flow
Common Collector Common Collector
n
p
n
n
p
n
forward bias
reverse bias
forward bias
reverse bias
BJT Topologies – Basic Bias 34 Young Won Lim
07/14/2017
Common Collector (2)
E
B
C
E
B
C
Electron Flow Current Flow
Common Collector Common Collector
n
p
n
n
p
n
n
p
n
n
p
n
BJT Topologies – Basic Bias 35 Young Won Lim
07/14/2017
BJT Bias
n p nE C
n p n
B E
B
C E
B
C
n
p
n
n
p
n
n
p
n
n
p
n
E
B
C E
B
C
E C
B
++
+
+
+
+
– –
–
–
– –
Common CollectorCommon EmitterCommon Base
V BE V CB
V BE V CE V CB V CE
BJT Topologies – Basic Bias 36 Young Won Lim
07/14/2017
Common Emitter (2)
Electron Flow
n p n
E C
Current Flow
n p n n p n
B
Young Won Lim07/14/2017
References
[1] http://en.wikipedia.org/[2] J.H. McClellan, et al., Signal Processing First, Pearson Prentice Hall, 2003