5 sedra ch 05 mosfet revision

1. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 19/21/2020
MOS Field-Effect
Transistors (MOSFETs)
Chapter 5

2. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 29/21/2020
MOS Field Effect Transistors
1. Device Structure and Physical Operation
2. Current-Voltage Characteristics
3. MOSFET Circuits at DC
4. Applying the MOSFET in Amplifier Design
5. Small Signal Operations and Models
6. Basic MOSFET Amplifier Configurations
7. Biasing the MOSFET Amplifier Circuits
8. Discrete-Circuit MOS Amplifiers
9. The Body Effect and other Topics

3. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 39/21/2020
MOS Field Effect Transistors
1. Device Structure and Physical Operation
2. Current-Voltage Characteristics
3. MOSFET Circuits at DC
4. Applying the MOSFET in Amplifier Design
5. Small Signal Operations and Models
6. Basic MOSFET Amplifier Configurations
7. Biasing the MOSFET Amplifier Circuits
8. Discrete-Circuit MOS Amplifiers
9. The Body Effect and other Topics

4. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 49/21/2020
DEVICE STRUCTURE AND
PHYSICAL OPERATION

5. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 59/21/2020
Device Structure
NMOS

6. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 69/21/2020
Device Structure

7. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 79/21/2020
Operation with Zero Gate Voltage

8. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 89/21/2020
Operation as vDS Is Increased

9. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 99/21/2020
Triode Region:
Saturation Region:
1
2
D n OV DS DSi k v v v
 
   
21
2
D n OVi k v
OV GS Tv v V  '
n n
W
k k
L

Derivation of the iD-vDS Relationship
DS OVv v
DS OVv v
 
1DS
DS n OV
D
v
r k V
i

 
1
DS
n OV
r
k V

𝑘 𝑛
′ = 𝜇 𝑛 𝐶 𝑂𝑥

10. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 109/21/2020
The p-Channel MOSFET

11. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 119/21/2020
The Complementary MOS or CMOS

12. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 129/21/2020
CURRENT-VOLTAGE
CHARACTERISTICS

13. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 139/21/2020
Circuit Symbols

14. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 149/21/2020
The iD-vDS Characteristics

15. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 159/21/2020
The iD-vGS Characteristics

16. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 169/21/2020
The iD-vGS Characteristics
21
2
D n OVi k v
Sat

17. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 179/21/2020
The iD-vGS Characteristics

18. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 189/21/2020
The iD-vGS Characteristics

19. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 199/21/2020
The Effect of vDS on iD
 21
1
2
D n OV DSi k v v 
21
1
2
DS
D n OV
A
v
i k v
V
 
  
 
A
O
D
V
r
I

1
ConstantGS
D
O
DS V
di
r
dv

 
  
 

20. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 209/21/2020
Large-signal Equivalent Circuit Model

21. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 219/21/2020
Characteristics of the p-Channel MOSFET
tV ve@
SG tv V
DS OVv vTriode Region:
Saturation Region:
OV GS tv v V 
DS OVv v
1
2
D p OV DS DSi k v v v
 
   
'
p p
W
k k
L

21
1
2
DS
D p OV
A
v
i k v
V
 
  
 

22. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 229/21/2020
Terminal Voltage-Region Relationship

23. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 239/21/2020
MOSFET CIRCUITS AT DC

24. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 249/21/2020
Triode Region:
Saturation Region:
1
2
D n OV DS DSi k v v v
 
   
OV GS Tv v V 
Derivation of the iD-vDS Relationship
'
n n
W
k k
L

 21
1
2
D n OV DSi k v v 

25. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 259/21/2020
Example 5.3
0.4
0.5?
?
3.2k 
0.7tV 
0 
DR  5
2.5 0.5
0.4


5
S SR V : DS tQ V V Sat 
 21
1
2
D n OV DSi k v v 
21
0.4 3.2
2
OVv  
0.5 0.5OVv    
0.7 0.5 1.2GSv   
 1.2 2.5 1.3
3.25
0.4 0.4
SR
  
  

26. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 269/21/2020
Example 5.5
1k 
1tV ?DSR 
1
2
D n OV DS DSi k v v v
 
   
0.39Di mA
12.4DR k 
Triode?
?
VD = + 0.1 V

27. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 279/21/2020
APPLYING THE MOSFET IN
AMPLIFIER DESIGN

28. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 289/21/2020
The Voltage Transfer Characteristics
 
21
2
D n GS ti k v V 
Ov DD D DV R i DSv
 
21
2
o DD n D GS tv V k R v V  
| |DS B GS B tV V V 
2 1 1
| n D DD
GS B t
n D
k R V
V V
k R
 
 

29. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 299/21/2020
| I IQ
O
V v v
I
dv
A
dv

Operation as a Linear Amplifier
?

30. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 309/21/2020
GS GS gsv V v 
 
21
2
D n GS ti k v V 
 
21
2
D n gs GS ti k v V V    
2 21 1
2 2
D n OV n OV gs n gsi k V k V v k v  
21
2
D n gs OVi k v V   
D D di I i 
The Signal Current in the Drain Terminal
21
2
d n OV gs n gsi k V v k v 
To achieve linearity:
21
2
n gs n OV gsk v k V v=
2gs OVv V=
d n OV gsi k V v
m n OVg k V
d m gsi g v

31. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 319/21/2020
| GS GS
D
m v v
GS
di
g
dv

The Signal Current in the Drain Terminal
To achieve linearity:
2gs OVv V=
d m gsi g v
21
2
| GS GS
n OV
m v V
GS
d k v
g
dv

 
 
 
m n OVg k V

32. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 329/21/2020
Separating the DC Analysis and the Signal Analysis
Under the small-signal approximation:
ac is superimposed on dc.
Apply superposition
Solution: dc then ac

33. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 339/21/2020
Small-Signal Models for the MOSFET

34. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 349/21/2020
 ||d
V m D O
gs
v
A g R r
v
  
The Voltage Gain
di

di 

35. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 359/21/2020
The Trans-Conductance gm
m n OVg k V
2m n Dg k I
2 D
m
OV
I
g
V


36. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 369/21/2020
Example 5.10
?VA 
?inR 
_max ?iv 
1.5tV V
0.25nk 
50AV V

37. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 379/21/2020
DC Solution
Neglect Modulation
21
1
2
DS
D n OV
A
V
I k V
V
 
  
 
15D D DV R I  1.06DI mA4.4DV V
21
2D n OVI k V
 
21
1.5
8
D DI V 
Example 5.10

38. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 389/21/2020
AC Solution
Example 5.10

39. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 399/21/2020
AC Solution
m n OVg k V  0.25 4.4 1.5  0.725 /mA V
A
o
D
V
r
I

50
1.06
 47 k 
Example 5.10
? ?

40. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 409/21/2020
AC Solution
10 1047
10 M
=4.52PR
VA  iv  ov 
vA 
o
i
v
v
m gs Pg v R 
Example 5.10
?
gsv
m Pg R  0.725 4.52   3.3 
m gs P
gs
g v R
v
 

41. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 419/21/2020
AC Solution
=10 M
Example 5.10
_
+
gsv
GR
GR m gsg v PR || GR
1
m gs
G
g v
R
 
 
 
gs
G
v
R

42. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 429/21/2020
AC Solution
10 1047
10 M
=4.52PR
Example 5.10
inR  i
i
v
i
i
i o
G
v
v v
R

 
 
 
1
1
G
o
i
R
v
v


1
1
G
v
R
A


i
G
i o
v
R
v v


1
4.3
in GR R 2.33M

43. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 439/21/2020
Largest Allowable Input Signal Vi
For linearity:
Example 5.10
No Triode: D G tv v V 
_min _maxD G tv v V 
ˆ ˆD v i G i tV A v V v V   
ˆ ˆ4.4 3.3 4.4 1.5i iv v   
ˆ 0.34iv V
G D DV I V  
2 OVV
5
OVV
gsv  0.58
4.4 1.5
5


44. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 449/21/2020
The T Equivalent-Circuit Model

45. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 459/21/2020
Drain-to-Source Resistance ro
The T Equivalent-Circuit Model

46. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 469/21/2020
Example 5.11

47. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 489/21/2020
Small-Signal Equivalent Circuit Model
Without Body Effect

48. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 499/21/2020
BIASING IN MOS
AMPLIFIER CIRCUITS

49. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 509/21/2020
Biasing in MOS Amplifier Circuits
• Fixing VG and Connecting a Resistance in the
Source
• Fixing VGS
• Using a Constant Current Source
• Using a Drain to Gate Feedback Resistor

50. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 519/21/2020
Large Variation in MOS Parameters
Fixing VGS
1. Manufacturing
2. Temperature

51. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 529/21/2020
Fixing VG and Connecting a Resistance in the Source
Degeneration Resistance
Basic Arrangement

52. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 539/21/2020
Single Supply Practical Implementation
Rule of Thumb

53. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 549/21/2020
AC Coupling

54. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 559/21/2020
Two Supply Practical Implementation
Rule of Thumb

55. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 569/21/2020
Using a Drain-to-Gate Feedback Resistor
DD GS D DV V I R 
GS DD D DV V I R 
-ve Feedback
↑ 𝐼 𝐷 →↓ 𝑉𝐺𝑆 →↓ 𝐼 𝐷

56. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 579/21/2020
Using a Constant-Current Source
?
 
21
2
D GS tI k V V 

57. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 589/21/2020
?
 
2
1
1
2
D n GS tI k V V Q
12 D
GS t
n
I
V V
k
  
1Q DD SS GS
D
V V V
I
R
 

1
DD SS GS
D
V V V
R
I
 
 
Current Mirror
 
2'
2
2
1
2
Q D n GS t
W
I I k V V
L
 
   
 
2
Ref
1
W
I L
WI
L
 
 
  
 
 
 

58. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 599/21/2020
ICs use constant-current source biasing only!

59. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 609/21/2020
BASIC MOSFET AMPLIFIER
CONFIGURATIONS

60. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 619/21/2020
The Basic Configurations

61. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 629/21/2020
The Common-Source Amplifier
Coupling
Isolates DC
biasing
from RL
and RSig
By Pass
Capacitor
Input
Coupling
Equivalent Circuit

62. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 639/21/2020
The Common-Source Amplifier Equivalent Circuit

63. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 649/21/2020
The Common-Source Amplifier Equivalent Circuit

64. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 659/21/2020
The Common-Source Amplifier with a Source
Resistance
Neglect for Simplicity
?

65. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 669/21/2020
The Common-Source Amplifier with a Source
Resistance

66. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 679/21/2020
The Common-Source Amplifier with a Source
Resistance
VA 
 ||
1
D L
S
m
R R
R
g

 
 
 
R
 
 
||
1
m D L
m S
g R R
g R

 

VOA 
 1
m D
m S
g R
g R



67. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 689/21/2020
The Common-Source Amplifier with a Source
Resistance

68. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 699/21/2020
The Common-Gate Amplifier

69. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 709/21/2020
The Common-Gate Amplifier
Neglect gmb and rO for Simplicity
DR
o
v
i
v
A
v

?
1
i i
m
v i
g

?
 ||o i D Lv i R R
 ||m D Lg R R
voA  m Dg R

70. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 719/21/2020
The Common-Gate Amplifier
iA 
isA 
D
D L
R
R R
1

71. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 729/21/2020
Current Followersig ii i
The Common-Gate Amplifier

72. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 739/21/2020
The Common-Drain or Source-Follower Amplifier

73. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 749/21/2020
The Common-Drain or Source-Follower Amplifier

74. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 759/21/2020
inR 
The Common-Drain or Source-Follower Amplifier
GR

75. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 769/21/2020
outR 
The Common-Drain or Source-Follower Amplifier

76. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 779/21/2020
The Common-Drain or Source-Follower Amplifier
outR 

77. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 789/21/2020
The Common-Drain or Source-Follower Amplifier
outR 
1
/ /o
m
r
g

78. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 799/21/2020
vA  o
i
v
v
||
1
||
o L
o L
m
r R
r R
g


?o Lr R
1
L
v
L
m
R
A
R
g


The Common-Drain or Source-Follower Amplifier
Vi

79. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 809/21/2020
The Depletion-Type MOSFET

80. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 819/21/2020
The Depletion-Type MOSFET

81. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 829/21/2020
The Depletion-Type MOSFET

82. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 839/21/2020
The Depletion-Type MOSFET

83. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 849/21/2020
The Depletion-Type MOSFET

84. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 859/21/2020
The Depletion-Type MOSFET

85. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 869/21/2020
The Role of the Substrate-The Body Effect
VB
VDR

86. Copyright  Muhammad A M Islam.SBE202A Device Structure and Physical Operation 879/21/2020
Small-Signal Equivalent Circuit Model
With Body Effect