Upload
vuthien
View
279
Download
7
Embed Size (px)
Citation preview
Lecture #5 FET Biasing & AC Analysis Instructor: Dr. Ahmad El-Banna N
ov
em
ber
2014
J-601-1448 Electronic Principals
Integrated Technical Education Cluster At AlAmeeria
© A
hmad
El-B
anna
Agenda
2
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Construction and Characteristics
FET Biasing
Design and Troubleshooting
JFET small signal Model
FET Amplifier Networks
Practical Applications
Note! Same concepts of the BJT, so we will just overview the FET transistors.
CONSTRUCTION AND CHARACTERISTICS
3
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Construction
4
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
• One of the most important characteristics of the FET is its high input impedance.
• FETs are more temperature stable than
BJTs, and FETs are usually smaller than BJTs, making them particularly useful in integrated-circuit (IC) chips.
Construction..
5
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
N-channel
Characteristics & Equations
6
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Depletion-Type MOSFET
7
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
• There is no direct electrical connection between the gate terminal and the channel of a MOSFET.
• It is the insulating layer of SiO2 in the MOSFET construction that accounts for the very desirable high input impedance of the device.
Depletion-Type MOSFET
8
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Other MOSFETS
9
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
• VMOS AND UMOS POWER MOSFETs • CMOS
• MESFET
FET BIASING
10
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
FIXED-BIAS CONFIGURATION
11
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Example
12
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Voltage-Divider Bias
13
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Example
14
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
DESIGN AND TROUBLESHOOTING
15
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Design Example
16
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Troubleshooting
17
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
The level of VDS is typically between 25% and 75% of VDD .
The continuity of a network can be checked simply by measuring the voltage across any resistor of the network.
JFET SMALL SIGNAL MODEL
18
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
JFET small signal Model
19
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Fixed-Bias Configuration
20
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
phase shift of 180° between input and output voltages.
VOLTAGE-DIVIDER CONFIGURATION
21
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
FET AMPLIFIER NETWORKS
22
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Design FET Amplifier Network
23
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
24
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Summary Table
25
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Cascaded Configuration
26
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
PRACTICAL APPLICATIONS 27
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Three-Channel Audio Mixer
28
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
Motion Detection System
29
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na
• For more details, refer to:
• Chapter 6,7,8, Electronic Devices and Circuits, Boylestad.
• The lecture is available online at:
• https://speakerdeck.com/ahmad_elbanna
• For inquires, send to:
30
J-601
-144
8 , L
ec#5
, Nov
201
4 ©
Ahm
ad E
l-Ban
na