Fundamentals of the Metal-Oxide-Semiconductor

Field-Effect Transistor and its applications

.

The Basic MOSFET Operation

N-channel enhancement-mode MOSFET

G

S

D

B

Circuit symbol

I-V relationship

DSDD VgI

'nnD Q

L

Wg 單位面積反轉層上的電荷大小:'

nQ

TGSDS

TDSGS

VVsatV

VsatVV

enhancement n-channel MOSFET

222 DSDSTGS

oxnD VVVV

L

CWI

2

2 TGSoxn

D VVL

CWI

Non-saturation: Saturation:

depletion n-channel MOSFET

TGSoxn

D

DSDSTGSoxn

D

VVL

CWI

VVVVL

CWI

222

TGSoxn

D

TGSoxn

D

VVL

CWI

VVL

CWI

2

22

transconductance

GS

Dm V

Ig

DSoxn

GS

DmL V

L

CW

V

Ig

TGSoxn

GS

Dms VV

L

CW

V

satIg

Non-saturation:

Saturation:

Inherent resistances and capacitances in MOSFET

Small-signal equivalent circuit of a CS

CMOS technology

CMOS inverter

I-V relationship….11.3.3

1. The current in the channel is due to drift rather than diffusion.

2. There is no current through the gate oxide.

3. A gradual channel approximation is used in which . This approximation means that Ex is essentially a constant.

4. Any fixed oxide charge is an equivalent charge density at the oxide-semiconductor interface.

5. The carrier mobility in the channel is constant.

x

E

y

Exy