Download - Chapter-8 FET Amplifiers
-
8/3/2019 Chapter-8 FET Amplifiers
1/29
Chapter 8:
FET Amplifiers
-
8/3/2019 Chapter-8 FET Amplifiers
2/29
IntroductionIntroduction
Excellent voltage gain g nput mpe ance
Low-power consumption
Good frequency range
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
22
-
8/3/2019 Chapter-8 FET Amplifiers
3/29
FET SmallFET Small--Si nal ModelSi nal Model
TransconductanceTransconductance
e re a ons p o a c ange n D o e correspon ng c ange n
VGS is called transconductancetransconductance
ranscon uc ance s eno e gm an g ven y:
DI=GSV
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
33
-
8/3/2019 Chapter-8 FET Amplifiers
4/29
Gra hical Determination ofGra hical Determination of
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
44
-
8/3/2019 Chapter-8 FET Amplifiers
5/29
Mathematical Definitions ofMathematical Definitions of
GS
Dm
V
Ig =
P
GS
P
DSSm
V
V1
V
2Ig
P
DSSm0
V
2Ig =
Where VGS =0V
P
GSm0mV
V1gg
DSS
D
P
GS
I
I
V
V1 =
Where
DSS
Dm0
P
GSm0m
Ig
V1gg =
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
55
-
8/3/2019 Chapter-8 FET Amplifiers
6/29
FET Im edanceFET Im edance
Input impedance:Input impedance:
iZ
do1
rZ =Output Impedance:Output Impedance:
os
where:
constantVD
DSd GSI
r =
yos= admittance parameter listed on FET specification sheets.
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
66
-
8/3/2019 Chapter-8 FET Amplifiers
7/29
FET AC Equivalent CircuitFET AC Equivalent Circuit
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
77
-
8/3/2019 Chapter-8 FET Amplifiers
8/29
CommonCommon--Source CS FixedSource CS Fixed--Bias CircuitBias Circuit
The input is on the gate and the
output is on the drain
There is a 180 phase shiftbetween input and output
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
88
-
8/3/2019 Chapter-8 FET Amplifiers
9/29
Input impedance:Input impedance:
Gi RZ =Out ut im edance:Out ut im edance:
dDo r||RZ =
10RrDo Dd
)R||(rgV
V
A Ddmo
v
Dd 10RrDm
i
ov Rg
V
VA
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
99
-
8/3/2019 Chapter-8 FET Amplifiers
10/29
CommonCommon--Source CS SelfSource CS Self--Bias CircuitBias Circuit
This is a common-source amplifier
configuration, so the input is on the gate
and the output is on the drain
There is a 180 phase shift betweeninput and output
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1010
-
8/3/2019 Chapter-8 FET Amplifiers
11/29
CalculationsCalculations
Input impedance:Input impedance:
Gi =Out ut im edance:Out ut im edance:
Ddo R||rZ =
10RrDo Dd
)R||(rgA Ddmv Voltage gain:Voltage gain:
Dd 10RrDmv RgA
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1111
-
8/3/2019 Chapter-8 FET Amplifiers
12/29
CommonCommon--Source (CS) SelfSource (CS) Self--Bias CircuitBias Circuit
Removing Cs affects
the gain of the circuit.
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1212
-
8/3/2019 Chapter-8 FET Amplifiers
13/29
CalculationsCalculations
RZ =Input impedance:Input impedance:
Output impedance:Output impedance:
10RrDo Dd
RZ
Dmo RgV Voltage gain:Voltage gain:
d
SDSm
iv
r
RRRg1
V ++=
RV)R(R01r
Smiv SDdRg1V
++
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1313
-
8/3/2019 Chapter-8 FET Amplifiers
14/29
CommonCommon--Source (CS) VoltageSource (CS) Voltage--Divider BiasDivider Bias
This is a common-source
amplifier configuration, so the
in ut is on the ate and theoutput is on the drain.
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1414
-
8/3/2019 Chapter-8 FET Amplifiers
15/29
ImpedancesImpedances
Input impedance:Input impedance:
21i R||RZ =
Ddo R||rZ =
10RrDo DdRZ
)R||(rgA Ddmv
Dd 10RrDmv RgA
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1515
-
8/3/2019 Chapter-8 FET Amplifiers
16/29
--
-
configuration, the input is on the
gate, but the output is from the
.
There is no phase shift between
npu an ou pu .
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1616
-
8/3/2019 Chapter-8 FET Amplifiers
17/29
ImpedancesImpedances
Input impedance:Input impedance:
Gi =
Output impedance:Output impedance:
mSdo
g
1||R||rZ =
Sd 10Rrm
So g||RZ
)R||(rg1
)R||(rg
V
V
A Sdm
Sdm
i
o
v +
10rSm
Sm
i
ov dRg1
Rg
V
VA +
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1717
-
8/3/2019 Chapter-8 FET Amplifiers
18/29
CommonCommon--Gate CG CircuitGate CG Circuit
and the output is on the
drain.
There is no phase shift
between input and output.
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1818
-
8/3/2019 Chapter-8 FET Amplifiers
19/29
CalculationsCalculations
Input impedance:Input impedance:
++=
dm
DdSi
rg1
Rr||RZ
Dd 10Rrm
Sig
||RZ
dDo r||RZ =10rDo d
RZ
+ DDm rR
Rg
+=
d
Div
r
R1
VA 10RrDmv Dd
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
1919
-
8/3/2019 Chapter-8 FET Amplifiers
20/29
DD--T e MOSFET AC E uivalentT e MOSFET AC E uivalent
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2020
-
8/3/2019 Chapter-8 FET Amplifiers
21/29
--
gm and rd can be found inthe specification sheet for
the FET.
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2121
-
8/3/2019 Chapter-8 FET Amplifiers
22/29
-- --
There is a 180 phase shiftbetween input and output.
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2222
-
8/3/2019 Chapter-8 FET Amplifiers
23/29
CalculationsCalculations
Input impedance:Input impedance:
)R||(rg1
R||rRZ
Ddm
DdFi +
+=FR
Out ut im edanceOut ut im edance::
DdDdF r,rDmRg1
>+
DdFo ||Rr||RZ =10RrR||rRDo RZ >
Voltage gainVoltage gain::
)R||r||(RgA DdFmv Dmv D10Rd,rD||RdrFRRgA >
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2323
-
8/3/2019 Chapter-8 FET Amplifiers
24/29
-- --
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2424
-
8/3/2019 Chapter-8 FET Amplifiers
25/29
CalculationsCalculations
Input impedanceInput impedance::
21i R||RZ =
Ddo R||rZ =u pu mpe ance:u pu mpe ance:
10rDod
)R||(rgA Ddmv
Dd 10RrDmvg
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2525
-
8/3/2019 Chapter-8 FET Amplifiers
26/29
Summar TableSummar Table
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
more2626
-
8/3/2019 Chapter-8 FET Amplifiers
27/29
Summar TableSummar Table
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2727
-
8/3/2019 Chapter-8 FET Amplifiers
28/29
Check the DC bias voltages:Check the DC bias voltages:
If not correct check power supply, resistors, FET. Also check to ensure
that the coupling capacitor between amplifier stages is OK.
.
Check the AC voltages:Check the AC voltages:
,
stage
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2828
-
8/3/2019 Chapter-8 FET Amplifiers
29/29
Practical A licationsPractical A lications
ThreeThree--Channel Audio MixerChannel Audio Mixer
Silent SwitchingSilent Switching
Phase Shift NetworksPhase Shift Networks
Motion Detection S stemMotion Detection S stem
Copyright 2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458 All rights reserved.
Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky
2929