Elektronika Dasar Bipolar Junction Transistor

2. Bipolar Junction Transistor

BJT Transistor Modeling
Amplication in the ac domain

Steady current established by a dc supply Effect of a control element on
the steady-state flow of the
electrical system

2. Bipolar Junction Transistor

Transistor circuit

ac analysis

Replacing all DC and capacitors by a short-circuit equivalent

small-signal ac analysis
\
The Importance Parameters

Two-port system

Input impedance:

Output impedance:

2. Bipolar Junction Transistor

The output impedance is determined at the output terminals looking back into the system with

the applied signal set to zero.

Voltage Gain

Current Gain

2. Bipolar Junction Transistor

Determining the loaded current gain

Phase relationship
For the typical transistor amplifier, the input and output signals are either 180° out
of phase or in phase.

THE re TRANSISTOR MODEL

BJT transistor amplifiers are referred to as current-controlled devices.

Common Base Configuration

re model

2. Bipolar Junction Transistor

Typical values of the Zo are in the mega ohm range

Defining Zo.

(Vo and Vi are in phase)

2. Bipolar Junction Transistor

Determining Zi

Impact of re on input impedance.

2. Bipolar Junction Transistor

If the applied signal is set to zero, then Ic is 0 A,resulting

(Vo and Vi are 1800 out of phase)

2. Bipolar Junction Transistor

Two-port system

The term “term” or h-parameter was chosen because the mixture of variables( V and I)

Hybrid input equivalent circuit

Hybrid output equivalent circuit

2. Bipolar Junction Transistor

Complete hybrid equivalent circuit
Short-circuit input–impedance parameter:

Open-circuit reverse transfer voltage ratio parameter:

Short-circuit forward transfer current ratio parameter:

Open-circuit output admittance parameter:

The common emitter configuration: Ii =Ib, Io=Ic,Vi=Vbe,Vo=Vce
Ie= Ib + Ic

Common-emitter configuration
The common base configuration: Ii=Ie, Io=Ic,Vi=Veb,Vo=Vcb
Ie= Ib + Ic

2. Bipolar Junction Transistor

Common base configuration
Since hr is normally a relatively small quantity and resistance determined by 1/ho is often large
enough, resulting

Hybrid versus re model

Common-emitter Configuration

2. Bipolar Junction Transistor

The current source of the standard hybrid equivalent circuit is pointing down rather than in
the actual direction as shown in the re model

GRAPHICAL DETERMINATION OF THE h-PARAMETERS

2. Bipolar Junction Transistor

2. Bipolar Junction Transistor

2. Bipolar Junction Transistor

Complete hybrid equivalent circuit for a transistor

1.5kW

BJT Small-Signal Analysis

10 0 Ib

33mA / V

2. Bipolar Junction Transistor

re model
1. Common Emitter (CE) Fixed-Bias Configuration

Effect of ro
Zo= ro||Rc

1
Rc

1 1
+
Rc ro

βIb=

Io=
ro
Io
roβ
βIb → =
ro+ Rc
Ib ro+ Rc

2. Bipolar Junction Transistor

Av=

−ro∨¿ Rc
ℜ

Ai=

Io Io Ib
ro. β
roβ
=
=
( ≅ 1 ) → Ai=
Ii Ib Io ro+ Rc
ro+ Rc

(

)

CE Voltage-Divider Bias Configuration

R’=R1||R2=

R 1+ R 2
¿
R 1. R 2
¿

Zi=R’|| βre

Zo = Rc
Av =

ℜ
¿
−Rc
¿

Effect of ro

Zo = ro||Rc
−ro∨¿ Rc
Av =
ℜ
ro+ Rc
¿
Io ro. β
=
¿
Ib

Ai =
Or

Ai =

ro+Rc R '
Io Io Ib
¿ R ' + βre
=

=
Ii Ib Io
ro . β
¿
Rc
¿

−Av

Zi
¿

1
βre

Ib
R'
Ii → = '
1
1
Ii R + βre
+
βre R '
Io
Io = βIb → Ib =β
Io Io Ib
βR'
Ai = Ii = Ib Ii = '
R + βre

Ib =

2. Bipolar Junction Transistor

Unbypassed

β +1)Ib RE = ( β
Vi = Ib β re +Ie RE = Ib β re +
¿

Zb =

Vi
=β
Ib

re +(

β +1)RE =

¿
β¿

re + RE)

re +

β +1) RE)Ib
¿

(for β >>1)

Ib =

RB+ Zb
¿
1
1
Ib RB
+
Ii → =
¿
Zb RB
Ii
¿
1
Zb
¿
≅ β RE (for RE >>
Zi = RB || Zb

re)

Io =
Ai =

βIb →

Io Io Ib β . RB
=
=
Ii Ib Ii RB+Zb
or

Zo = Rc

Io
=β
Ib

2. Bipolar Junction Transistor

Vi

Ib = Zb
−Io . Rc=−βIb Rc
Vo −Rc
Vi
Vo= −β ( Zb ) Rc → Av= Vi = ℜ+ ℜ
Vo=

Effect of ro
For typical parameter values the effect of ro can be ignored
Bypassed
If RE is bypassed by an emitter capacitor CE, then
Zb = β . re

Av =

−Rc
ℜ

Common Collector ( Emitter Follower) Configuration

2. Bipolar Junction Transistor

COMMON-BASE CONFIGURATION

2. Bipolar Junction Transistor

Vi
Vo= Io Rc = ( Ic )Rc = α Ie.Rc = α r e Rc → Av
Ie ≅ Ii ( for RE>>re)
Io = −Ic=−α Ie ¿−α Ii → Ai=−α ≅−1

( )

Effect of

(since α ≅ 1 ¿

ro

For typical parameter values the effect of ro can be ignored

APPROXIMATE HYBRID EQUIVALENT CIRCUIT

common-emitter

hie =
re

β

re

hie =

β

re

common-base

hoe = 1/ro

hfb =

α

hib =

2. Bipolar Junction Transistor



Common Emitter (CE) Fixed Bias Configuration

Zi =RB
Zo=RC

||h

ie

(

VO = -IoRC = hfe Ib RC = - hfe
Ib ≅ Ii
Io = hfe Ii

Vi
hie

)

RC

AV = -

h fe Rc
hie

( for RB >> hie
hfe

Effect of ro
Hoe =

1
ro
Zo =

re =
Av = -



1
|| Rc
hoe

hie
hfe
hfe(

1
∨¿ Rc)
hoe
hie

CE Voltage – Divider – Bias Configuration

2. Bipolar Junction Transistor

 CE Emitter –Bias Configuration
Unbypassed



Common Collector (Emitter Follower) Configuration

2. Bipolar Junction Transistor

 Common Base Configuration

Zi = RE||h
Zo = Rc
Ie =
Vo =
Ai =

ib

Vi
hib

h ib
¿
−Io . Rc=−( hfb . Ie ) Rc=¿−hfb

Io
=hfb
Ii

( hibVi ) Rc → Av= −hfb¿. Rc

2. Bipolar Junction Transistor

System Aprroach- Effect Of Rs And RL
Fixed Bias
V

CC

RC

RB

RC

Zi = RB|| β
Zo = Rc

re

Vo −RL∨¿ Rc
=
Vi
re
Zi
= Zi+ Rs Av
Io
Zi
Ii = Is → Ai = Ii =−Av RL

Av =

Voltage Divider Bias

CE Unbypass Emitter Bias

Vi =

Zi
Vi
Vs →
Zi+ Rs
Vs

=
Vo

Av s = Vs =¿

RL

Zi
Zi+ Rs
Vi Vo
Vs Vi

2. Bipolar Junction Transistor

Emitter Follower Network

R’E = RE||RL

Vs – Ib .Rs

β
+1)Ib R’E = 0 → Ib
– Ib βre−¿

=

Vs
Vs
≅
Rs+ βre+ ( β+1 ) R ' E Rs+ β ( ℜ+ R ' E)

Ie

=

βI b

Rs
'
+ ℜ+ R E
β
Vs
¿ ¿

R' E
Vo =

Rs
+ ℜ+ R' E
β

vs

Rs
+ ℜ¿
β
Common Base Network
Zo = RE ||

(

→

Avs =

R' E
Rs
+ ℜ+ R' E
β
βre+ ( β +1 ) R' E ≅ β ( ℜ+ R' E )

Zi = RB ||Zb

Zb =

2. Bipolar Junction Transistor

RL∨¿ Rc
Av ≅ r e

Philips Semiconductors
specification

Product

NPN general purpose transistors
107;BC 108;BC;109

BC

PINNING

FEATURES



Low current (max. 100mA)
Low voltage ( max. 45 V)

PIN

DESCRIPTION

1

emitter

2

base

3

Collector,connected the case

APPLICATIONS

General purpose switching and amplification

2. Bipolar Junction Transistor

DESCRIPTIONS
NPN transistor in a TO-18;SOT 18 metal package
PNP complement : BC177

Characteristic
T = 25 C, unless other wise specified
symbol
parameters
conditions
IcBc
Collector cut-off current
IE = 0; VCB = 20 V
IE = 0; VCB = 20 V; T = 125
IeBc
hFE

hFE

Emitter cut-off current
DC current gain
BC 107A; BC108A
BC107B; BC108B; BC109B
BC109C; BC109C

C
Ic = 0; VEB = 5 V
Ic = 10μA;VcE = 5 V

DC current gain
BC 107A; BC108A
BC107B; BC108B;BC109B
BC109C; BC109C

Ic = 2

VCEsat

Collector emitter saturation
voltage

Ic = 10 mA; IB = 0,5 mA
Ic = 100 mA; IB = 5 mA

VBEsat

Base emitter saturation
voltage

Ic = 10 mA; IB = 0,5

mA;VcE = 5 V

mA;note 1

min
-

type
-

max
15
15

unit
nA

-

-

50

nA

40
10
0

90
15
0
27
0

-

11
0
20
0
42
0
-

18
0
29
0
52
0
90
20
0

-

70
0
90
0

22
0
45
0
80
0
25
0
60
0
-

Ic = 100 mA; IB = 5 mA;note

1
VBE

Base emitter voltage

Ic = 2 mA; VcE = 5 V; note 2
Ic = 10 mA; VcE = 5 V; note
2

55
0
-

62
0
-

Cc

Collector capacitance

IE = ie = 0; VCB =10 V; f = 1

-

2.5

70
0
77
0
6

μA

mV
mV
mV
mV

mV
mV
pF

2. Bipolar Junction Transistor

Ce

Emitter capacitance

fT

transition frecuency

F

Noise figure
BC109B;BC109C

F

Noise figure
BC 107A; BC108A
BC107B; BC108B; BC108C
BC109B; BC109C
NOTES

MHZ
IC= ic = 0; VEB =0,5 V; f = 1
MHZ
IC= 10mA; VCB =5 V; f = 100
MHZ
Ic = 200μA;VcE = 5 V;Rs = 2 kΩ
f = 30 Hz to 15.7 kHz
Ic = 200μA;VcE = 5 V;Rs = 2
kΩ;
F = 1kHz;B = 200Hz

-

9

-

pF

10
0

-

-

MH
z

-

-

4

dB

-

-

10
4

dB
dB

1. VBEsat decrease by about 1.7 mV/K with increasing temperature
2. VBE decrease by about 2 mV/K with increasing temperature

2. Bipolar Junction Transistor