1. EE 2303/001 - Electronics I Summer 2001 Lecture 15
Professor Ronald L. Carter
Spring 2001
L15 July 23

2. n-channel enhancement MOSFET in ohmic region
0< VT< VG
Channel
VS = 0
0< VD< VDS,sat
EOx,x> 0 n+
e-e- e- e- e- n+
Depl Reg
p-substrate
Acceptors
VB < 0
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3. Conductance of inverted channel
Q’n = - C’Ox(VGC-VT)
n’s = C’Ox(VGC-VT)/q, (# inv elect/cm2)
The conductivity sn = (n’s/t) q mn
G = sn(Wt/L) = n’s q mn (W/L) = 1/R, so
I = V/R = dV/dR, dR = dL/(n’sqmnW)
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4. Basic I-V relation for MOS channel
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5. I-V relation for n-MOS (ohmic reg)ID
non-physical
ID,sat
saturated
VDS,sat
VDS
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6. Universal drain characteristicID
VGS=VT+3V
9ID1
ohmic
saturated, VDS>VGS-VT
VGS=VT+2V
4ID1
VGS=VT+1V
ID1
VDS
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7. Characterizing the n-ch MOSFETVD ID D G S B VT
VGS
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8. Low field ohmic characteristics
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9. MOSFET circuit parameters
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10. MOSFET circuit parameters (cont)
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11. Substrate bias effect on VT (body-effect)
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12. Body effect data
Fig 9.9, Device Electronics for Integrated Circuits, 2nd ed., by Richard S. Muller and Theodore I. Kamins, Wiley, NY, 1986
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