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

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 L15 July 23

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) L15 July 23

Basic I-V relation for MOS channel L15 July 23

I-V relation for n-MOS (ohmic reg) ID non-physical ID,sat saturated VDS,sat VDS L15 July 23

Universal drain characteristic ID VGS=VT+3V 9ID1 ohmic saturated, VDS>VGS-VT VGS=VT+2V 4ID1 VGS=VT+1V ID1 VDS L15 July 23

Characterizing the n-ch MOSFET VD ID D G S B VT VGS L15 July 23

Low field ohmic characteristics L15 July 23

MOSFET circuit parameters L15 July 23

MOSFET circuit parameters (cont) L15 July 23

Substrate bias effect on VT (body-effect) L15 July 23

Body effect data Fig 9.9, Device Electronics for Integrated Circuits, 2nd ed., by Richard S. Muller and Theodore I. Kamins, Wiley, NY, 1986 L15 July 23