Slide điện tử từ trường lecture 7 metal oxide semiconductor field effecttransistors (mosfets)

Structure of enhancement-type CMOS transistor... Channel length modulation as Early effect... Microelectronic Circuit by meiling CHEN 27 CuuDuongThanCong.com https://fb.com/tailieudientu

characteristic

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+

− V DS

− + V GS

Reverse V GS ↗ Ædepletion region ↗Æchannel ↘ÆI↘

Reverse V GS ↗↗Æ depletion region ↗↗Æchannel ~0 ÆI=0 (pinch off)

DSS

V = 0 ⇒ ≡

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S G

N-channel

D

S G

P-channel symbol of JFET

depletion-type MOSFET (n-channel)

V

V GS = −

+ + + + + +

Depletion

Structure of enhancement-type NMOS transistor

insulator

m W

nm t

m L

50

~ 2

3

~ 1 0

10

~ 10

m W

nm t

m L

50

~ 2

3

~ 1 0

0

) (

, 0

DS D

t GS

GS

R I

V V

V

if

V

DS

t GS

↑⇒

>

D DS

t GS

I V

t GS

I V

C ox : capacitance per unit gate area

Total capacitance at dx

] )

(

C dq

CV Q

0 0

)

( 2

1

] )

( 2

1 )

[(

] 2

1 )

[(

) ( ] )

( [

) ( ] )

( [

) ( ] )

( [

) ( ] )

( [

) ( )

(

] )

( [

t GS ox

n

D

t GS t

GS ox

n D

t GS DS

DS DS

t GS ox

n

D

t GS

ox n

v L

D

t GS

ox n D

t GS

ox n D

t GS

ox n

n n

t GS

ox

V

v L

W C i

V v

V

v L

W C i

V v

v

v v

V

v L

W C

i

x dv V x v v

W C dx

i

x dv V x v v

W C dx

i

dx

x dv V x v v

W C i

i

dx

x dv V x v v

W C i

dx

x dv x

E dt

dx

V x v v

Wdx C

dq

dt

dx dx

dq dt

μ

μ

μ μ

Saturation region

Saturation region

Ohmic region

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Structure of enhancement-type CMOS transistor

Microelectronic Circuit by

meiling CHEN

21

EMOSFET operation mode

• Ohmic (triode) region

t GS

DS

t GS

DS

V v

V v

v

V v

SG

t SG

SD

t SG

SD

V V

v

V v

v

V v

v

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NMOSFET current-Voltage characteristic

Ohmic region

Cutoff region

] )

( 2

[ 2

2

DS DS

t GS o

n

L

w C

L

w C

w C

Saturation region large-signal model

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Channel length modulation (as Early effect)

Microelectronic Circuit by

meiling CHEN

27

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Microelectronic Circuit by

meiling CHEN

29

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