Transistors Bipolars

Bipolar Junction Transistor (BJT)

Bipolar Transistors

N

P

P

N

P

N

Emitter

Base

Collector

Emitter

Base

Collector

Emitter

Collector

Base

Emitter

Collector

Base

2 junctions

JEB

JCB

JBE

JBC

JEB/JBE ON JCB/JBC ON

Saturation

JEB/JBE OFF JCB/JBC OFF

Cut-Off

JEB/JBE ON JCB/JBC OFF

Forward Active

JEB/JBE OFF JCB/JBC ON

Reverse Active

WORKING REGIONS

Bipolar transistors: Ebers-Mll Model

Forward Active

holes

electrons

Recombination

ic

Ie=Ien+Iep

ien

ib

iep

Ie = ic + ib

ic

Ebers-Mll Model

JBE ON JBC OFF

JBE

JBC

E

C

B

JBE

JBC

IF

IR

aR IR

aF IF

JBE

JBC

IF

aF IF

N

N

P

IE = IF

IC = aF IF

IB = IF (1-aF)

Ic = 0

Bipolar transistors: Ebers-Mll Model

JBE

JBC

IF

IR

aR IR

aF IF

IE = IF - aR IR

IC = aF IF - IR

IB = IF (1-aF) + IR (1-aR)

Injection Model

E

JBE

JBC

IBE

IBC

bF IBE - bR IBC

B

C

E

Transport Model

IE = (bF+1) IBE bR IBC

IC = bF IBE (bR+1) IBC

IB = IBE + IBC

IBE = IF (1-aF)

IBC = IR (1-aR)

IE = (bF+1) IF (1-aF) bR IR (1-aR)

(bF+1) (1-aF) = 1

bF = - 1 =

bR (1-aR) = aR

bR =

C

B

JBE

JBC

IBE

IBC

bF IBE - bR IBC

B

C

E

Bipolar transistors: Ebers-Mll Model

Forward Active

Reverse Active

JBE

IBE

B

C

E

bF IBE

VBE 0,7 V

JBC

IBC

B

C

E

bR IBC

VBC 0,5 V

IC = bF IBE= bF IB

IE = bR IBC= bR IB

bF > bR

JBE

JBC

IBE

IBC

bF IBE - bR IBC

B

C

E

Bipolar transistors: Ebers-Mll Model

Cut-Off

Saturation

IC = IB= IE = 0

B

C

E

JBC

IBC

B

C

E

bF IBE - bR IBC

JBE

IBE

VBC 0,5 V

VBE 0,7 V

C

E

B

VBE 0,7 V

VCE 0,2 V

JBE

JBC

IBE

IBC

B

C

E

Bipolar transistors: High frequency model

bF IBE - bR IBC

To be considered only when working at high frequency

+

VCE

-

+

VBE

-

Bipolar transistors

According the model

FORWARD ACTIVE

VCE

IC

IB1

IB2

IB3

CUT-OFF

SATURATION

IC

IB

+

VCE

-

+

VBE

-

VCE

IC

IB1

IB2

IB3

Bipolar transistors

VCE = VCB + VBE

considering VBE constant

VCE => VCB

Emitter

Base

Collector

Recombination decreases

IC

Base width modulation

(EARLY EFFECT)

IC = IB

Forward active region

IC

IB

Recombination

ic

VCE

IB1

IB2

Bipolar transistors

IC = IB

Forward active region

-VA

Safe Operating ARea

VCE

IC

ICmax

VCE0max

Pd = VCE Ic + VBE IB VCE Ic Pdmax

SOAR

VEB VEB0max

VCB VCB0max

To avoid junction rupture

To avoid excesive heating by Joule effect

2N222

Metal-Oxide-Semiconductor Field Effect Transistor

(MOSFET)

MOS transistor

Metal

Oxide

Semiconductor

Bulk

Gate

Drain

Source

CHANEL N

CHANEL P

CHANEL N

Enhancement

-

-

-

-

-

-

-

-

Bulk

Gate

Drain

Source

P

-

-

-

-

ID

VGS

VT

-

-

-

-

-

-

-

-

Bulk

Gate

Drain

Source

CHANEL N

P

Depletion

ID

VGS

VT

-

-

-

-

-

-

-

-

-

-

-

-

16

Bulk

Gate

Drain

Source

CHANEL P

N

ID

VGS

VT

VDS VGS -VDS =VT

VDS = VGS -VT

Saturation

ID

VT

VGS

ID

VT

VGS

DEPLETION

22

CHANEL P

ENHANCEMENT

DEPLETION

ID

VT

VGS

ID

VT

VGS

VDS

ID

VGS

VDS

ID

VGS

VT

VGS

ID

ID

VT

VGS

CHANEL N

ENHANCEMENT

DEPLETION

K = (A/V2)

VT

W and L

L

technological parameters

Circuit designer fixed parameters

W

C

B

E

C

W

(

)

(

)

DS

2

T

GS

D

V

1

V

V

L

W

2

k

I

+

-

=