1

S. Lineykin, Introduction to electronics Slide [53]22-Apr-09

Common Base Configuration

Input characteristics: iE vs. vEB with

vCB=const

Output characteristic: iC vs. vCB with

IE=const

Picture from ref [2]

S. Lineykin, Introduction to electronics Slide [54]22-Apr-09

Common Base Terminal characteristics [2]

Picture from ref [2]

ICBO

( )E

CBOCFB

I

IIh

−≡≡α

99.0107 ≈≈⇒≈ −

E

CCBO

I

IAI α

BCE IIIKCL +=:

( )CBOCBC IIII ++= α

( ) ( ) CEOBCBO

BC III

II +=−

+−

= βαα

α

11

S. Lineykin, Introduction to electronics Slide [55]22-Apr-09

Ebers-Moll model for active region (large signal)

2

S. Lineykin, Introduction to electronics Slide [56]22-Apr-09

Ebers-Moll model for active region (large signal)

S. Lineykin, Introduction to electronics Slide [57]22-Apr-09

Analytical model

Ebers-Moll model of

Transistor (active region)

( )( ) ( )

( ) ( )11

11

1

−=−=

−=−=

−=

TVBEv

TVBEv

TVBEv

TVBEv

TVBEv

eI

eIi

eI

eIi

eIi

CSBSB

CSESE

CSC

β

α

S. Lineykin, Introduction to electronics Slide [58]22-Apr-09

Internal Feedback Effect and Output Resistance

3

S. Lineykin, Introduction to electronics Slide [59]22-Apr-09

H-parameters in CB-mode

0

2

2

22

0

1

2

21

0

2

1

12

1

1

11

|;|

|;|

|;|

||

01

02

01

002

→

→

→

=≡

=≡

=≡

=≡

=

=

=

→=

e

cb

e

cb

i

cb

cobi

v

e

cfbv

i

eb

cbrbi

v

e

ebibv

v

ih

v

ih

i

ih

i

ih

v

vh

v

vh

i

vh

i

vh

definitionsMeasurement method

S. Lineykin, Introduction to electronics Slide [60]22-Apr-09

Small-signal h parameters

S. Lineykin, Introduction to electronics Slide [61]22-Apr-09

Common Emitter Terminal characteristic [2]

Picture from ref [2]

4

S. Lineykin, Introduction to electronics Slide [62]22-Apr-09

Small signal hie, hoe

S. Lineykin, Introduction to electronics Slide [63]22-Apr-09

Early Voltage

Early effect:

Depletion layer of BC-Junction increases with vCE => current increases

The density of electrons in BE-Junction increases with VBE => current increases

( ) ( )2211 CECE vWvW >

+=

A

CEVv

SCV

veIi T

BE

1

S. Lineykin, Introduction to electronics Slide [64]22-Apr-09

Small signal hfe

100||0

≈=≡ = Q

b

cv

b

cfe

di

di

i

ih

ce

5

S. Lineykin, Introduction to electronics Slide [65]22-Apr-09

Small signal: gm

[ ]Ω==≈=== /104.0,1|| mC

T

C

e

Q

be

eQ

be

cm gmAIfor

V

I

rdv

di

dv

dig

αα

( ) ( )Ω≈=

+≈

+===≡ = khmAIfor

V

I

rdv

di

dv

di

hi

vh ieC

T

C

e

Q

be

eQ

be

b

ie

v

b

beie ce

6.2,11

11

1

1||

1;|

0βββ

α

hie

ie

mh

gβ

=

S. Lineykin, Introduction to electronics Slide [66]22-Apr-09

Small signal: hre

mv

vh

ci

ce

bere 1|

0≈≡ =

S. Lineykin, Introduction to electronics Slide [67]22-Apr-09

Small signal: 1/hoe (ro)

0|

1=≡=

bi

c

ceo

oe i

vr

h

Picture from ref [3]

Ω≈=+

== krmAIforVV

I

dv

dih

oC

CEA

CQ

ce

coe

100,1,|

6

S. Lineykin, Introduction to electronics Slide [68]22-Apr-09

Large and small signal model for active region

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [69]22-Apr-09

Small signal model (T)

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [70]22-Apr-09

π-model

Picture from ref [3]

7

S. Lineykin, Introduction to electronics Slide [71]22-Apr-09

Small Signal Models of BJT

S. Lineykin, Introduction to electronics Slide [72]22-Apr-09

IV Transistor: Elementary circuits

Common Emitter (CE)

Common Base (CB)

Common Collector (CC)

S. Lineykin, Introduction to electronics Slide [73]22-Apr-09

Picture from ref [3]

8

S. Lineykin, Introduction to electronics Slide [74]22-Apr-09

1. CE amplifier

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [75]22-Apr-09

CE-exampleVCC=10V, IC=1mA, VO=5V

VA=100V, β=100V, ICS

=10fA

Find:

•Graphical solution

•IE, VBB, IB, RC

•Small signal parameters

•Draw a small signal equivalent circuit

•Solve the circuit

S. Lineykin, Introduction to electronics Slide [76]22-Apr-09

CE – graphical solution

9

S. Lineykin, Introduction to electronics Slide [77]22-Apr-09

Q-point solution, IE, VBB, IB, RC

mVI

IVV

mAIII

uAI

I

kI

VVR

CS

CTBB

CBE

CB

C

OCCC

656ln

01.1

10

5

=

=

=+=

==

Ω=−

=

β

S. Lineykin, Introduction to electronics Slide [78]22-Apr-09

Small signal equivalent circuit parameters

( )

0

105

104.0

6.21

26

100

≈

Ω=+

=

Ω≈=

Ω=⋅+=

Ω≈≈

==

re

C

CEAo

e

m

eie

E

Te

fe

h

kI

VVr

rg

krh

I

Vr

h

α

β

β

S. Lineykin, Introduction to electronics Slide [79]22-Apr-09

Small Signal equivalent circuit

( )

kAAA

hRr

rh

i

iA

RgRrgv

vA

ivp

ferR

Co

ofe

s

oi

CmrRCom

s

ov

oC

oC

20100200

100|

200|||

=−⋅−=≡

−=−=+

−=≡

−=−=−=≡

<<

<<

10

S. Lineykin, Introduction to electronics Slide [80]22-Apr-09

Small Signal equivalent circuit

( ) Ω==

Ω=≈=

Ω==

krRR

kRRrR

khR

oCO

CCoo

iein

100

5||

6.2

S. Lineykin, Introduction to electronics Slide [81]22-Apr-09

2. CC amplifier

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [82]22-Apr-09

CC-exampleVCC=10V, IC=1mA, VO=5V

VA=100V, β=100V, ICS

=10fA

Find:

•Graphical solution

•IE, VBB, IB, RC

•Small signal parameters

•Draw a small signal equivalent circuit

•Solve the circuit

11

S. Lineykin, Introduction to electronics Slide [83]22-Apr-09

CE-graphical solution

S. Lineykin, Introduction to electronics Slide [84]22-Apr-09

Q-point solution, IE, VBB, IB, RC

0

656.5ln

01.1

10

5

95.4

=

=

+=

=

=

=−=

Ω===

C

CS

CTEEBB

E

B

OCCCE

C

O

E

OE

R

VI

IVRIV

mAI

uAI

VVVV

kI

V

I

VR

α

S. Lineykin, Introduction to electronics Slide [85]22-Apr-09

Small signal equivalent circuit parameters

( )

0

105

104.0

6.21

26

100

≈

Ω=+

=

Ω≈=

Ω=⋅+=

Ω≈≈

==

re

C

CEAo

e

m

eie

E

Te

fe

h

kI

VVr

rg

krh

I

Vr

h

α

β

β

12

S. Lineykin, Introduction to electronics Slide [86]22-Apr-09

Small Signal equivalent circuit

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [87]22-Apr-09

Rin

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [88]22-Apr-09

RO

Picture from ref [3]

13

S. Lineykin, Introduction to electronics Slide [89]22-Apr-09

3. CB amplifier

Picture from ref [3]

S. Lineykin, Introduction to electronics Slide [90]22-Apr-09

CB-exampleVCC=10V, IC=1mA, VO=5V

VA=100V, β=100V, ICS

=10fA

Find:

•Graphical solution

•IE, VBB, IB, RC

•Small signal parameters

•Draw a small signal equivalent circuit

•Solve the circuit

S. Lineykin, Introduction to electronics Slide [91]22-Apr-09

CB – graphical solution

14

S. Lineykin, Introduction to electronics Slide [92]22-Apr-09

Q-point solution, IE, VBB, IB, RC

OEECE

CS

CTBB

CBE

CB

C

OCCC

VVV

mVI

IVV

mAIII

uAI

I

kI

VVR

+=

=

=

=+=

==

Ω=−

=

656ln

01.1

10

5

β

S. Lineykin, Introduction to electronics Slide [93]22-Apr-09

Small signal equivalent circuit parameters

( )

0

105

104.0

6.21

26

100

≈

Ω=+

=

Ω≈=

Ω=⋅+=

Ω≈≈

==

re

C

CEAo

e

m

eie

E

Te

fe

h

kI

VVr

rg

krh

I

Vr

h

α

β

β

S. Lineykin, Introduction to electronics Slide [94]22-Apr-09

Small Signal Equivalent Circuit

15

S. Lineykin, Introduction to electronics Slide [95]22-Apr-09

CB: Ai

S. Lineykin, Introduction to electronics Slide [96]22-Apr-09

CB: Rin, Ro