simply emphasise how to derive h parameter conversion formula of CC and CB from h parameters of CE. Generally BJT manufactures give CE parameters with data sheets and we should be able to convert them to the configuration we are involving. As well as the pure conversion formula we also helpful approximate h parameter conversion formulas with considarable approximations.

1. Small-Signal Transistor
Amplifiers
h Parameter Model
Conversion Formulas
H.A.S. KALHARA
sadeeshkalhara1@gmail.com

2. Conversion Formulas
CC parameters from CE parameters
! !
To satisfy the condition , place a short circuit across the output terminals.
using KVL we write,
FIGURE 1 - Circuit for obtaining CC parameters from CE
parameters
h11 =
v1
i1 v2=0
hic =
vbc
ib vec=0
vbc −hrevce =ibhie
vce =0
∴vbc =ibhie
vbc
ib
=hic =hie
vce = 0

3. !
using KCL we write,
h21 =
i2
i1 v2=0
h22 =
i2
v2 i1=0
hfc =
ie
ib vec=0
ib +hfeib +ie =0
ie
ib
=− 1+hfe( )=hfc
hrc =
vbc
vec ib=0
= vbe +vec
vec ib=0
ib = 0,vbe = hrevce =−hrevec
∴hrc =1−hre
hoc = ie
vec ib=0
ib = 0,
∴vec =ie ⋅
1
hoe
ie
vec
= hoc = hoe
h12 =
v1
v2 i1=0

4. CB parameters from CE parameters
To satisfy the condition , place a short circuit across the output terminals.
using KVL for input loop,
using KVL for output loop,
h11 =
v1
i1 v2=0
hib =
veb
ie vcb=0
vcb = 0
veb +hrevce =−ibhie
vce =−veb
veb ⋅ 1−hre
#$ %&=−ibhie
veb −
hfeib
hoe
=−
ic
hoe
vebhoe +
hfe 1−hre
"# $%veb
hie
=−ic
FIGURE 2 - Circuit for obtaining CB parameters from CE
parameters

5. using KCL,
!
Leaving the input port open to satisfy the condition ,
and also note that,
h21 =
i2
i1 v2=0
hfb = ic
ie vcb=0
hfb =
− vebhoe +
hfe 1−hre( )
hie
"
#
$
$
%
&
'
'
veb hoehie + 1+hfe( ) 1−hre( )"
#
%
&
hie
hfb =
−hfe 1−hre( )−hiehoe
1+hfe( ) 1−hre( )+hoehie
h12 =
v1
v2 i1=0
hrb =
veb
vcb ie=0
ie = 0
ib =−ic
ie = − ic +ib( )
ie = vebhoe +
hfe 1−hre
"
#
$
%veb
hie
+
veb 1−hre
"# $%
hie
ie =
veb hoehie + 1+hfe( ) 1−hre( )"
#
$
%
hie
veb
ie
=
hie
hoehie + 1+hfe( ) 1−hre( )"
#
$
%
= hib

6. using the KVL for input loop,
using the KVL for output loop,
using derived formulas above,
veb +hrevce =−hieib = hieic
but,
vce =
ic
hoe
+
hfeic
hoe
∵ib =−ic
"# $%
veb =ic hie −
hre
hoe
−
hfehre
hoe
"
#
&
&
$
%
'
'
vcb +
hfeib
hoe
+hrevce =ic hie +
1
hoe
!
"
#
$
%
&
∴vcb −
hfeic
hoe
+hre
ic
hoe
+
ichfe
hoe
!
"
#
#
$
%
&
&
=ic hie +
1
hoe
!
"
#
$
%
&
∴vcb =ic hie +
1
hoe
+
hfe
hoe
−
hre
hoe
−
hrehfe
hoe
!
"
#
#
$
%
&
&
hrb
=
veb
vcb ie=0
hrb
=
ic hie −
hre
hoe
−
hfehre
hoe
"
#
$
$
%
&
'
'
ic hie +
1
hoe
+
hfe
hoe
−
hre
hoe
−
hrehfe
hoe
"
#
$
$
%
&
'
'
hrb =
hiehoe −hre 1+hfe( )
hoehie + 1+hfe( ) 1−hre( )

7. summary of the h-parameter conversion equations
!
hib =
hie
hoehie + 1+hfe( ) 1−hre( )
hrb =
hiehoe −hre 1+hfe( )
hoehie + 1+hfe( ) 1−hre( )
hfb =
−hfe 1−hre( )−hiehoe
1+hfe( ) 1−hre( )+hoehie
hob =
hoe
hoehie + 1+hfe( ) 1−hre( )
hic = hie
hrc =1−hre
hfc = −(1+hfe )
hoc = hoe
CB
CC
h22 =
i2
v2 i1=0
hob = ic
vcb ie=0
hob =
ic
ic hie +
1
hoe
+
hfe
hoe
−
hre
hoe
−
hrehfe
hoe
"
#
$
$
%
&
'
'
hob =
hoe
hoehie + 1+hfe( ) 1−hre( )

8. Approximate conversion formulas
conversion formulas derived above can be simplified substantially by neglecting terms that are very
small compared to other terms in the expression. For example, for CE configuration
and hold, and also for CC and hold.
reference:
1)Electronics Devices and circuits - Theodore F.Bogart.
2)Electronics Devices and circuits - principles and applications - N.P. Deshpande
hib =
hie
1+hfe
hrb =
hiehoe
1+hfe
−hre
hfb = −
hfe
1+hfe
hob =
hoe
1+hfe
hic = hie
hrc =1
hfc = −(1+hfe )
hoc = hoe
CB
CC
hre ≪1
hfe +1≫ hiehoe hrc ≈ 1hoc ≈ 0