analog elctronics
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Presentation on HybridPresentation on HybridCommon Transistor ModelCommon Transistor Model
Amit GuptaAmit Gupta
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The hybrid commonThe hybrid common
emitter transistor modelemitter transistor model
The CE configuration is the most importantThe CE configuration is the most important
practical configuration.practical configuration.The analysis using the hybrid modelThe analysis using the hybrid model
is not very difficult and gives accurateis not very difficult and gives accurate
result at all the frequencyresult at all the frequency
The resistive components in this circuit canThe resistive components in this circuit can
be obtained from the low frequency h-be obtained from the low frequency h-
parameters.parameters.
All the components resistor andAll the components resistor and
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Components in the hybridComponents in the hybrid
modelmodel In the hybrid model there are 4In the hybrid model there are 4
terminals namely C,B,E and B out ofterminals namely C,B,E and B out of
which C, B and E have their normalwhich C, B and E have their normal
meaning and they are usermeaning and they are user
accessible terminalsaccessible terminals
B is not a user accessible terminalsB is not a user accessible terminals
it is called virtual base terminals.it is called virtual base terminals.
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Expression for TransistorExpression for Transistor
Transconductance (gTransconductance (gmm))
( )
)3......(
)1(.exp
)2.....(
tan
)1.....(tan
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EEB
E
Em
EB
E
EB
ECO
m
ECOC
CE
EB
Cm
VSinceVV
Ig
V
I
V
II
g
eqntoinressionthisngSubstituti
III
transistorofregionactivetheIntconsVfor
V
IgcectransconduThe
othereachtoshortedareEmitterandcollectorThe
=
=
=
=
=
=
=
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)7........(
)6........(
tan
)5........(
)3(.
)4........(
tan
q
kTV
isetemperaturofequivalentvolt
thebutbiasedforwardisdiodeemittorthebecause
I
Vr
isetemperaturequivalentvoltinceresisemittorThe
rg
eqntoinvaluethisngSubstituti
IVr
isceresisemittertheBut
T
E
Te
e
m
E
Ee
=
=
=
=
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T
c
m
T
ccom
ccoE
T
Em
e
V
I
g
V
IIg
IIIBut
V
Ig
eqntoinrofvaluethengSubstituti
=
=
=
)5.(
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The Input Conductance (gThe Input Conductance (gbebe ))
fe
meb
eb
eb
ebm
b
cfe
ebbmebmc
ebbeb
ebb
h
ggso
Rgceconducputinbut
RgI
Ih
isgaincurrentcircuitshortthehenceRIgVgI
iscurrentcollectorcircuitshortthetherefore
RIV
isRthroughflowwillIcurrentbasethetherefore
=
=
==
==
=
>
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'
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'
cb'cb'
1tan
)*(
*
rr,valuecomponenttheFrom
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The feedback conductanceThe feedback conductance
(g(gbcbc ))
ebcbre
re
reebcbre
ebcbreebre
cbeb
eb
ce
ebre
cecbeb
eb
eb
cecbeb
b
ce
ebre
rrh
h
hrrh
rrhrh
rr
r
V
Vh
Vrr
rV
Vacrossdividerpotentialaformrandrthatevidentisit
IforV
Vh
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'''
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'
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'
1)1(
)1(
*
0
=
=
=+
+==
+
=
==
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ebre
eb
eb
re
ce
eb
ebce
ebcb
eb
ebb
ce
bcb
ghceconducfeedback
g
r
andh
V
V
rVVg
r
VIbut
V
Ig
'
'
'
'
'
''
'
'
'
*tan
1
=
==
=
=
=
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Base spreading resistanceBase spreading resistance
(r(rbbbb ))
||||
)||(
)||(
)||(
.
'''
''
'''''
'''
'''
''
''
C
Tfe
C
Tfe
bbebbbie
ebiebb
ebbbcbebbbie
b
cbebbbbb
b
beie
ebcbeb
cbeb
ebcb
I
Vh
I
Vhrrrh
rhr
rrrrrh
I
rrIrI
I
Vhhence
rrrso
rr
butothereachwithparallelinappearrandr
+=+=
=
++=
+==
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The Output conductanceThe Output conductance
(g(gcece ))
( )
( )
( )
getweneglectingsorrBut
rrhg
rVI
rr
VVhg
r
VI
getwevaluestheallngSubstitutirrVIandVhgVgIrVI
IIIButI
IVIh
cbeb
cbeb
rem
ce
ceC
cbeb
cecerem
ce
ceC
cbebceceremebmcece
C
b
ce
Coe
,
11
,
0
''
''
''
''3'21
121
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cbremoece
cbremceoe
cbcbcece
cb
rem
cece
Coe
cb
rem
ce
ceC
ghghgghggh
grandgrsubstitutenow
rhg
rV
Ih
rhg
rVI
'
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)/1()/1(
11
11
=++=
==
++==
++=
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