Slide điện tử từ trường lecture 4 bipolar junction transistors

characteristics Transistor= Tran sfer re sistor Two categories of transistor 1... Solid State Physics Group leader William Shockley saw the potential in this, and over the next few month

Lecture 04

Bipolar junction

transistors

(BJTs)

characteristics

Transistor= Tran sfer re sistor

Two categories of transistor

1 BJT

2 FET

- JFET

• 1971 : 4004 : 2 300 transistors

• 1978 : 8086 : 29 000 transistors

• 1982 : 80286 275 000 transistors

• 1989 : 80486 : 1,16 millions de transistors

• 1993 : Pentium : 3,1 millions de transistors

• 1995 : Pentium Pro : 5,5 millions de transistors

• 1997 : Pentium II : 27 Millions de transistors

• 2001 : Pentium 4 : 42 millions de transistors

• 2004 : Pentium 4 EE : 169 millions de transistors

In 1947, John Bardeen and Walter Brattain at AT&T's Bell Labs in

the United States observed that when electrical contacts were applied to

a germanium crystal, the output power was larger than the input Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge

of semiconductors

The first silicon transistor was produced by Texas Instruments in 1954 The first MOS transistor actually built was by Kahng and Atalla at Bell Labs in 1960

Structure of transistor

射極：代號E，寬度居三者之中，參雜濃度最濃。

基極：代號B，寬度最薄，參雜濃度最低。

集極：代號C，寬度最大，參雜濃度適中。

BJT operation mode

comparison

NPN transistor (Active mode)

En

Ep

1 J E forward-Biased : electrons injected from emitter into base ( i En ),

holes injected from base into emitter ( i Ep ).

2 In base: some electrons combined with holes ( i B2 ),

most of electrons diffused to collector ( i Cn ).

3 J C reverse-Biased : electrons swept across the depletion region ( i Cn ),

small saturation current in depletion region ( i Cp ),

Cn En

B

Cp B

Ep B

Cp Cn

C

Ep En

E

i i

i

i i

i i

i i

i

i i

i

−

=

− +

i i

Minority-carrier concentrations

T V BE V

e I

i C = S

T V BE V

e n

n p ( 0 ) = p 0

Ref to lecture 02 page24

A

n i E s

WN

D qn

A I

2

=

Ref to lecture 02 page22

C C

E

B C

E

S B

C B

i i

i

i i

i

e

I i

i i

T V BE V

α β

β β

V

e I

( + β

Active mode

NPN transistor (reverse active mode)

J E reverse and J C forward

(Active mode)

NPN transistor (Ebers_Moll mode) (for four modes)

+

NPN transistor (saturation mode)

J E Forward and J C Forward

T V BC V T

V BE V

e

I e

I i

R

S S

8 0

) (

2 0

)

V

Si V

V

i i

sat BE

sat CE

B C

=

=

Electronic Switch

Characteristic in Active mode

C E

B C

S C

i i

i i

e I

BE V

α

β 1

=

=

=

C E

B C

S C

i i

i i

e I

EB V

α

β 1

2 1

I

I V

mA

mA V

V

BE

T BE

717

0

1

2 ln 7

0

= +

mA mA

I I

I

k mA

V R

BE E

B C

E C

) 15 (

717

0

717

0

02

2 100

2 2

5 2

10

Exercise 5.11

C

E B

V and

find

V V

V V

given

, ,

7 1 ,

1

β α

+

= +

=

994

0 1

165 01

0

65 1

65 1

01

0 100

1

66

1 5

7 1 10

= +

β

B C

B E

C B E

I I

mA I

I I

mA k

I

mA k

I

Example : the transistor is work in saturation mode find the minimum β

I I

K I

V K

I I

K I

V V

V V

sat B sat

C sat

B

sat B sat

C sat

C

sat CE

sat BE

14 1

) (

8 0 10

14 1

) (

2 0 1

2 0

8 0

) ( )

( )

(

) ( )

( )

(

) (

) (

=

× +

+ +

×

=

× +

+ +

×

=

=

11 6

0

6 6

6 0

6 6

min

) (

) (

mA I

sat B sat C

k

6 1

Q1 : saturation Q2 and Q3 : cut off Q4 : saturation

D1 : on

k

6 1

k

6 1

Open collector

External R c

k

6 1

A

V

B

V

Output

Output

Output Input

Common-Base (CB)

Common-Emitter (CE)

Common-Collector (CC)

Transistor i C V BE Characteristic (change T)

T V BE

V

e I

Transistor i C V CB Characteristic (change i E )

α common-base current gain

Transistor i C V CE Characteristic (change I B )

β short circuit common-Emitter current gain

Transistor i C V CE Characteristic ( change V BE )

Given ,

J C depletion region effective base width Early

effect

1 0

−

r

Large-signal equivalent circuit ( Common Emitter in active mode )

K V

CE

C o

Transistor i C V CE Characteristic ( CE saturation mode)

i i

CE

B c

2 0

≈

≠ β

saturation mode equivalent circuit

Transistor breakdown

1 punch-through breakdown

V CE ↗↗→ J E and J C depletion region ↗ W B →0

2 Avalanche breakdown (Impact ionization)

1 large-scale Equivalent-circuit model

E C

B C

BC CE BE

i i

i i

V V

V V

V V

3 0

7 0

2 Ebers-moll Equivalent-circuit model

) 1 (

) 1 (

T V BE V

e I

i

e I

i

SC DC

SE DE

1 Saturation Equivalent-circuit model

V V

V V

V V

BC

CE

BE

6 0

~ 5 0

2 0

~ 1 0

8 0

~ 7 0

=

=

=