四、場效電晶體原理1. 電晶體簡介2. mosfet的操作原理(定性的描述
TRANSCRIPT
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1
5-1
1.
2. MOSFET(
3. MOSFET
4.
5. MOSFET
6. MOSFET2nd order effect
7. JFET
5-2
(transistor)(valve)
(a) (b)
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2
5-3
bipolar junction transistor, BJTfield effect transistor, FET
BJT pn
p+ nE
B
Cp
VEB VBC
E B C
E B C
5-4
FET (channel)
S
D
G
S
D
G
pFET nFET
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3
5-5
FET(Junction Field Effect Transistor, JFET)(Metal-Oxide-Semiconductor FET, MOSFET)
(Source)
(Drain)
(Gate)1
np+
(Gate)2
p+
tL p n+
(S)
(G)
n+
(Metal)
(Oxide)
(Semiconductor)(Body)
(D)
JFET\pn
MOSFETMOS
5-6
BJTpoint contact transistorBell Laboratory(John Bardeen, 1908-1991)Walter Brattain, 1902-1987William Shockley, 1910-19891947pn1956
FETBJTFETFET
1985K. von KlitzingMOSFET(Integer Quantum Hall Effect, IQHE)
1998(HEMT, high mobility transistor)Fractional Quantum Hall Effect)
, "", , , 2000.
2000(Zhores I. Alferov)(Herbert Kroemer)(Jack St. Clair Kilby)
HONOR LIST
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4
5-7
1964 for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle Charles Hard Townes, Nicolay Gennadiyevich Basov, Aleksandr Mikhailovich Prokhorov
1973L. Esaki (tunneling effect)
5-8
MOSFET
p n+
(S)
(G)
n+
(Metal)
(Oxide)
(Semiconductor)(Body)
(D)
(S)
(D)
(G)
(S)
(D)
(G)
(body)
nMOSFET(NMOS)
MOSFETMOSFET
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5
5-9
pn+
(S)
(G)
n+
(Oxide)
(Body)
(D)
C
n+
p
C
pnNMOS(cut off)
S D
GID
VGS
VDS>0
IG=0
VGS=0
5-10
pNMOS
pn+
(S)
(G)
n+
(D)
n+
0
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6
5-11
pn+
(S)
(G)
n+
(D)
VGS=Vt
Vt (threshold voltage)()
pn+
(S)
(G)
n+
(D)
VGS>VtVGS-Vt
n+
VGSVt
5-12
n+
n+
(1)(2)
(3)(4)
n+
(1)(2)
(3)(4)
CC
pn+
(S)
(G)
n+
(D)
VGSVt
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7
5-13
1.00.80.60.40.20
ID(mA)
0.40.20VDS (V)
VGS=4V
3.5V
3.0V
2.5V VGS2.0V= Vt
VDSMOSFETVGSVtVGS>VtDS
VDS DSI-V
MOSFET
5-14
n+
n+
C
VG
VS VDVGS VGD
n+
n+
C
VG
VSVD
VGSVGD
Vt
VDS
Vt
L
ID
VDS
ID
VDS
(a) (b)
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8
5-15
n+
n+
C
VG
VSVDVGS
VGD
VDS
Vt
n+
n+
C
VG
VS
VDVGS
VGD
VDS
Vt
L
X
ID
VDS
ID
VDS
VDSS
triode
saturation
(c) (d)
5-16
VGD= Vt(pinch off)VDSVGDVtDLL
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9
5-17
ID(mA)
VDS (V)
VDSS (=VGS-Vt)
VGS=4V
VGS=3.5V
VGS=3.0VVGS=2.5V
VGS2.0V
1086420
3210 4
(a)
(b)(c)
(d)
VGSMOSFET
(Analog Switch)
(VCCS)
)( GSD Vi
)( GSDS VR
5-18
MOSFET
MOSCoxMOStoxox
MOSL()W()MOS
(threshold voltage)VtMOSFET
(bias voltages)VGS, VDS, VS ,VB(body)
ID
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10
5-19
MOSFET
DSDS
DS
p n+
(S)
(G)
n+
(Metal)
(Oxide)
(Semiconductor)(Body)
(D)
L
W
(D)(S)
E(x)
Q(x)J(x)
ox
oxoxtGSox t
CVCQxQ === )()(
Q [C/m2]: Cox [F/m2]:
GS>Vt
5-20
LE DS=
[A/m]=[C/sm]L
VCEQQvJ DStGSoxnndn )( ===
iD DStGSnDStGSoxnnD VLWkV
LWCWJi )()( ===
=
=
)(
)(1
tGSnDS
DSDDS
tGSnD
DSDS
VL
Wkig
VL
Wki
r
(DS)
Process transconductance parameter: oxnn Ck = [A/V2]
DS
Aspect ratio: W/Llayout()LW
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11
5-21
DS
)21( DStGSox VC
iD
DS
n+
n+
C
G
SD
GSGD
DS
Vt
)( tGSox VC )( tGDox VC
DSDStGSnDSDStGSoxnD VLWkV
LWCi )
21()
21( ==
iD
iDDS(parabola)
Triode rigionGDVtDS GS-Vt
or
5-22
n+
n+
C
G
SGS
GD
DSVt
iD
DS
DSsat
GD=VtDSsat=GS-Vt
oriD
22 )(21)(
21
tGSntGSoxnD VLWkV
LWCi == Saturation region
GD VtDS GS-Vt
orDSDSsat iDDS(GS-Vt)
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12
5-23
iD (mA)
DS (V)
DSsat (=GS-Vt)GS=4V
GS=3.5V
GS=3.0VGS=2.5V
GS2.0V
1086420
3210 4
triode
saturation
cutoff
iDsat(mA)
GS (V)
1086420
0 321
Vt
4
OFF (S)
ON (S)
cutoff
saturation
triode
(S)
(D)
(G)
(S)
(D)
(G)
2
21
DSnD LWki =
2)(21
tGSnD VLWki =
5-24
n-channel MOSFET
iD (mA)
DS (V)
DSsat (=GS-Vt)GS=4V
GS=3.5V
GS=3.0VGS=2.5V
GS2.0V
1086420
3210 4
triode
saturation
cutoff
(S)
(D)(G)
iD
GSDS
iG=0
Open circuit
G
D
S
VCCS
Nonlinear resistance
GS2)(
21
tGSn VLWk
G D
S
GS
G D
S
rDS
)21(1 DStGSn
DSDS VL
Wkr
g ==
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13
5-25
IC
n+
p
C
n+
pn+
(S)
(G)
n+
(D)
VGS=Vt
Vt
CX
5-26
n+
C
X
pFlat-band condition
qs: Bending of surface potential
VGS =0
VGS=Vt
qVbi, B
qs
VGS
Q
Vt
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14
5-27
s
pn(built-in potential)
i
D
i
A
i
DAbi n
NkTnNkT
nNNkTqV lnlnln 2 +==
p n
(depletion region)(space charge region)
EC
EV
qVbi
Eg
xd
qp qnqnqp
+=
DA
bid NNq
Vx 112 Si
5-28
MOSFET
MetalOxide p-Si
Flat-band condition
EC
EV
MetalOxide p-Si
Threshold condition
EC
EV
qpqs
s =2 p
xd
qox
qVt
oxpoxstV +=+= 2
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5-29
Metal
Oxidep-Si
EC
EV
qpqs
xd
qox
E=0E=0 ESiEox
sox
tox
Vt
oxoxox tE=i
Aps n
NqkT ln22 ==
0
A
psd qN
x)2(2
=ESiSi
Sisoxox EE =Eox
ox
psA
A
ps
ox
A
ox
dAox
oxoxdASis
qN
qNqN
xqNE
ExqNE
)2(2
)2(2
=
=
=
==
ox
psAp
oxox
psAp
oxpt
CqN
tqN
V
)2(22
)2(22
2
+=
+=
+=
body(S)
5-30
ox
psApFB
oxox
psApFBt
CqN
V
tqN
VV
)2(22
)2(22
++=
++=
Vt
1. flat-band conditionVGS=0VFB VFB
2. Vt
3. Vt-2 mV/C
4. VGS=0MOSFET
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16
5-31
n+
C
X
pqs: Bending of surface potential
VGS=Vt qVbi,B
qVSB
5. (B)(S)VSBbody effect
qs +qVSB
[ ]ox
sApSBpt
ox
SBpsApFBt
CqN
VV
CVqN
VV
222
)2(22
0 ++=
+++=
Body-effect parameter
VSB
5-32
MOSFETMOSFETNMOS(n-channel MOSFET)PMOS (p-channel MOSFET)VGS=0(depletion type)(enhancement type)
iD
GS (V)
0
n-channelenhancement
n-channeldepletion
p-channelenhancement
p-channeldepletion
n-channelp-channeliD
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17
5-33
p-channel MOSFET
n p+
(S)
(G)
p+
(Metal)
(Oxide)
(Semiconductor)(Body)
(D)
(S)
(D)
(G)
(S)
(D)
(G)
(body)
iD
5-34
PMOS
iD (mA)
SD (V)
SDsat (=Vt-GS)GS=-4V
GS=-3.5V
GS=-3.0VGS=-2.5V
GS-2.0V
1086420
3210 4
triode
saturation
cutoff
(S)
(D)(G)
iD
GSSD
iG=0ox
oxoxtGSox t
CVCQxQ === )()(S
GSVt
DSDStGSp
SDSDGStoxpD
VL
Wk
VL
WCi
)21(
)21(
=
=
2
2
)(21
)(21
tGSp
GStoxpD
VL
Wk
VL
WCi
=
=
GDVt
GDVt
GS Vt
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18
5-35
n-channelenhancement
n-channeldepletion
p-channelenhancement
p-channeldepletion
S
Digital Circuit
5-36
Depletion-type MOSFETiD
GS (V)
0
n-channeldepletion
p-channeldepletion
IDSS
GS =0MOSFETMOSFET
MOSFETSi
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19
5-37
5-38
MOSFET2nd order effect
MOSFET
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20
5-39
Channel length modulation effect
n+
n+
C
VG
VS
VDVGS
VGD
VDS
Vt
L
X
VDSsat
L
DSSX(VDSsat)BJTEarly Effect
lambda AV=
1
5-40
GS
2)(21
tGSn VLWk
GD
S
ro
ro
DDA
o IIVr 1=
)1()(21 2
DStGSnD VLWki +=
2
1
2
1
LL
VV
A
A
-
21
5-41
(BS)
n+
C X
pFlat-band condition
qs: Bending of surface potential
VGS =0
VGS=Vt0 qVbi, B
n+
BS=0
n+
C X
pFlat-band condition VGS =0
qVbi, B
BS
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22
5-43
Vtk
1. Vt-2 mV/C
ox
bsBbFBt C
qNVV
)2(22
++=
i
Bb n
Nq
kT ln=
*
5.1
)()(me
TTTT
Ck
RR
ox
=
=
=
kT
2.
5-44
iDsat
GS (V)
iD
DS
T>T
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23
5-45
MOSFET
1. (NMOS)pn(avalanche breakdown)50100V
2. (NMOS)punch-through
3. 50V)
pn+
(S)
(G)
n+
(D)
CMOS(PMOS+NMOS)
npnpnp BJTlatch-up
5-46
MOSFET
MOSFET
pn+
(S)
(G)
n+
(D)
pn+
(S)
(G)
n+
(D)
(gate capacitive effect)
1. MOSFETtriodeWLCox CgsCgd
2. GS
oxgdgs WLCCC 21
==
032
=
=
gd
oxgs
C
WLCC
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24
5-47
3. 0== gdgs CC
(body)
oxgb WLCC =
4. Overlap capacitance:Lov0.1~0.2m13CgsCgdCov
oxovov CWLC =
p
n+n+
Lov
5-48
(Junction Capacitances)
(B)pn
0
0
0
0
1
1
VV
CC
VV
CC
DB
dbdb
SB
sbsb
+=
+=
NMOStox=20nm, L=2.4m, W=10m, Lov=0.15m, Csb0=Cdb0=40fF, |VSB|=|VDB|=2V
21.4 fF21.4 fF2.6 fF30.6 fF2.6 fF1.75 fF/m2
CdbCsbCgdCgsCovCox
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25
5-49
(Junction Field Effect Transistor, JFET)
(Source)
(Drain)
(Gate)1
n
p+
(Gate)2
p+
t
W
L
(S)
(D)
(G)
JFET input
(preamp)
5-50
S D
GID
VGS0
IG=0
1.00.80.60.40.20
ID(mA)
0.40.20VDS (V)
VGS=0V
-0.5V
-1.0V
-1.5V VGS-2.0V
Triode region:
pnnp+ntRDS
n(pinch off)(pinch-off voltage) Vp
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26
5-51
S D
G
n
p+
p+
L ID
VDS
S D
G
n
p+
ID
VDS
p+
VGSVDSIDVDS
5-52
S D
G
n
p+
ID
VDS
D
G
n
p+
p+
L
p+
S
ID
VGD=Vp
VGD
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27
5-53
XS D
qVDSS
L
n
VDSLLVDSXVpVDSVXS(=VDSS)VDSL
VDSVGS-Vp(=VDSS)VDSIDVDSIDVDS(constant-current)(saturation)
qVDS
5-54
iD(mA)
DS (V)
VDSS (=VGS-Vp)
VGS=0V
VGS=-0.5V
VGS=-1.0VVGS=-1.5V
VGS-2.0V
1086420
3210 4GS (V)
iD (mA)
1086420
-2 10-1
Vp
IDSS
)1(12
DSp
GSDSSD V
Ii +
=
Triode
=
2
12p
GS
p
GS
p
GSDSSD VVV
Ii
NJFETNMOS PJFETPMOS