Analog CMOS Integrated Circuit Design Set 2 - Courses - University ...

SM
Long Channel Current Equations - 3
dQ dQ dx
I Qd
velocity
dt dx dt
⋅ = × = =
• Current :
Velocity in terms of V(x):
dV
velocity = μ ⋅ E , E = −
dt
− dV ( x)
→ velocity = ( μ ⋅ )
dx
Qd in terms of V(x):
Qd ( x)
= −WC
ox ( VGS
−V
( x)
−VTH
)
• Current in terms of V(x):
L
∫ I dx = ∫WC
μ [ V
D
x=
0
dV ( x)
= WCox
[ VGS
−V
( x)
−VTH
] μ
dx
I D
n
V
DS
V = 0
• Long-channel current equation:
SM
ox
n
GS
−V
( x)
−V
W
1
I D = μ nC
ox [( VGS
−VTH
) VDS
− V
L
2
EECE 488 – Set 2: Background
SM 8
TH
2
DS
© Microelectronic Circuits, 2004 Oxford University Press
] dV
Long Channel Current Equations - 4
• If V DS ≤ V GS-V TH we say the device is operating in triode (or linear) region.
• Current in Triode Region:
EECE 488 – Set 2: Background
]
I = μ ⋅ C
• Terminology:
W
Aspect Ratio =
L
Overdrive Voltage = Effective
D
n
ox
W ⎡
1 2 ⎤
⋅ ⋅
⎢(
VGS
−VTH
) ⋅VDS
− ⋅VDS
L ⎣
2 ⎥
⎦
Voltage = V
GS
−V
TH
= V
eff
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