330 EE Lecture 16
Model Relationships CMOS Process Flow
Quiz 13
Determine the current ID for the following circuit. Assume the MOS transistor can be modeled by the basic square-law model with parameters VT=0.8V, COX=100A/V2 and COX=4fF/2 andB the device has dimensions W=10 and L=2.
And the number is ....
1
8
3
5
6
4
9
7
2
And the number is ....
1 7
4
9
3
8
6
2
5
Quiz 13
Determine the current ID for the following circuit. Assume the MOS transistor can be modeled by the basic square-law model with parameters VT=0.8V, COX=100A/V2 and COX=4fF/2 andB the device has dimensions W=10 and L=2.
Solution: 1. 2. 3. 4. Guess the device is operating in the Saturation Region Analyze the circuit with the device in this region Verify region of operation Repeat steps 1-3 if guess was not correct
Quiz 13
Solution: 2.
Determine the current ID for the following circuit. Assume the MOS transistor can be modeled by the basic square-law model with parameters VT=0.8V, COX=100A/V2 and COX=4fF/2 and the device has dimensions W=10 and L=2.
Analyze the circuit with the device in this region
0 W V VGS - VT - DS VDS ID = COX L 2 W (VGS - VT )2 COX 2L
VGS VT VGS VT VDS < VGS - VT VGS VT VDS VGS - VT
Quiz 13
Solution: 2.
Determine the current ID for the following circuit. Assume the MOS transistor can be modeled by the basic square-law model with parameters VT=0.8V, COX=100A/V2 and COX=4fF/2 and the device has dimensions W=10 and L=2.
Analyze the circuit with the device in this region
W 2 ID = COX ( VGS - VT ) 2L 2 -4 10 = 10 (1.5 - 0.8) 22 ID = 123 A
3. Verify region of operation
VGS ? VT
1.5V > 0.8V
VDS > ? VGS - VT
3V> 1.5V- 0.8V
Verifies!
Review from Last Time
n-Channel MOSFET Operation and Model
VDS VGS VBS
ID IG
IB
(VBS small)
Increase VDS even more Inversion layer disappears near drain Termed "saturation"region of operation Saturation first occurs when VDS=VGS-VT
ID=? IG=0 IB=0
Review from Last Time
Graphical Interpretation of MOS Model C W
I=
D OX
2L
V
2
DS
Triode Saturation
VGS4 VGS3 VGS2 VGS1
0 V W I = C V - V - V L 2 W (V - V ) C 2L
DS D OX GS T 2 OX GS T
V V
GS GS
Cutoff
T
T
DS
V V
V < V -V
DS GS
T
V V
GS
T
V V -V
DS GS
T
Model Status
Square-Law Model
VGS4 VGS3 VGS2 VGS1
0 V W I = C V - V - V L 2 W (V - V ) C 2L
DS D OX GS T 2 OX GS T
V V
GS GS
T
DS
V V
T
V < V -V
DS GS
T
V V
GS
T
V V -V
DS GS
T
Switch-Level Models
Drain Gate Source
Switch closed for VGS="1"
Switch-level model including gate capacitance and drain resistance
CGS and RSW dependent upon device sizes and process For minimum-sized devices in a 0.5u process
CGS 1.5fF
R sw
2K n - channel 6K p - channel
Considerable emphasis will be placed upon device sizing to manage CGS and RSW
Extended Square-Law Model
IG = 0 IB = 0
0 W V I = C V -V - V L 2 W C ( V - V ) (1 + V 2L
DS D OX GS T DS 2 OX GS T
V V
GS GS
T
V V
T
V < V -V
DS GS
T
DS
)
V V
GS
T
V V -V
DS GS
T
VT = VT0 +
( -V
BS
-
)
Model Parameters : {,COX,VT0,,,} Design Parameters : {W,L} but only one degree of freedom W/L
Short-Channel Model
0 W I = C (V - V ) V L W (V - V ) C L
2 2 D OX GS T 1 2 OX GS T
V V
GS GS
T
DS
V V
T
V < (V -V
DS 1 GS DS GS
T
)
2
V V
GS
T
V (V -V
1
T
)
2
is the velocity saturation index, 2 1 Channel length modulation () and bulk effects can be added to the velocity Saturation as well
BSIM model
BSIM Binning Model
- multiple BSIM models !
Model Relationships
Determine RSW and CGS for an n-channel MOSFET from square-law model In the 0.5u CMOS process if L=1u, W=1u (Assume COX=100AV-2, COX=2.5fFu-2,VT0=1V, VDD=3.5V, VSS=0)
0 W V I = C V -V - V L 2 W C (V - V ) 2L
DS D OX GS T 2 OX GS T
V V
GS GS
T
DS
V V
T
V < V -V
DS GS
T
V V
GS
T
V V -V
DS GS
T
When SW is on, operation is "deep" triode
Model Relationships
Determine RSW and CGS for an n-channel MOSFET from square-law model In the 0.5u CMOS process if L=1u, W=1u (Assume COX=100AV-2, COX=2.5fFu-2,VT0=1V, VDD=3.5V, VSS=0)
I C
D
OX
V = W W V -V - V C (V - V ) V L 2 L
DS GS T DS OX GS T
DS
R =
SQ
V I
DS
=
VGS =VDD
1 C
OX
D
W (V - V L
GS
T
)
VGS =3.5V
=
1 = 4K 1 ( E - 4) ( 3.5 - 1) 1
CGS= COXWL = (2.5fF-2)(12) = 2.5fF
Model Relationships
Determine RSW and CGS for an p-channel MOSFET from square-law model In the 0.5u CMOS process if L=1u, W=1u ( COX=2.5fFu-2,VT0=1V, VDD=3.5V, VSS=0) Observe n\ p3
0 W V I = C V -V - V L 2 W C (V - V ) 2L
DS D OX GS T 2 OX GS T
V V
GS GS
T
DS
V V
T
V < V -V
DS GS
T
V V
GS
T
V V -V
DS GS
T
When SW is on, operation is "deep" triode
Model Relationships
Determine RSW and CGS for an p-channel MOSFET from square-law model In the 0.5u CMOS process if L=1u, W=1u ( COX=2.5fFu-2,VT0=1V, VDD=3.5V, VSS=0) Observe n\ p3
0 W V I = C V -V - V L 2 W C (V - V ) 2L
DS D OX GS T 2 OX GS T
V V
GS GS
T
DS
V V
T
V < V -V
DS GS
T
V V
GS
T
V V -V
DS GS
T
When SW is on, operation is "deep" triode
Model Relationships
Determine RSW and CGS for an p-channel MOSFET from square-law model In the 0.5u CMOS process if L=1u, W=1u ( COX=2.5fFu-2,VT0=1V, VDD=3.5V, VSS=0) Observe n\ p3
I =C
D p
OX
V W W V -V - V C (V - V ) V L 2 L
DS GS T DS p OX GS T
DS
R =
SQ
V I
DS
=
VGS =VDD
1 C
p OX
D
W (V - V L
GS
T
)
VGS =3.5V
=
1 = 12 K 1 1 ( E - 4) ( 3.5 - 1) 3 1
CGS= COXWL = (2.5fF-2)(12) = 2.5fF Observe the resistance of the p-channel device is approximately 3 times larger than that of the n-channel device for same bias and dimensions !
Modeling of the MOSFET
Goal: Obtain a mathematical relationship between the port variables of a device. I = f (V ,V , V )
IB = f3 (VGS ,V DS , VBS ) IG = f2 (VGS ,V DS , VBS )
D 1 GS DS BS
Small-Signal Model
Goal with small signal model is to predict performance of circuit or device in the vicinity of an operating point Operating point is often termed Q-point
Small-Signal Model
y
YQ Q-point
XQ
x
Technology Files
Design Rules Process Flow (Fabrication Technology) (will
discussion next )
Model Parameters (will discuss in substantially more
detail after device operation and more advanced models are introduced)
This table discusses a p-well process flow, an n-well process flow is actually used in the following set of slides with straightforward modifications of this process flow.
Bulk CMOS Process Description
n-well process Single Metal Only Depicted Double Poly
Components Shown
n-channe...