MOSFET,MOSFET Amplifier Configuration,MOSFET Amplifier Inputoutput
MOSFET details
-
Upload
mani-kandan-k -
Category
Documents
-
view
43 -
download
1
description
Transcript of MOSFET details
![Page 1: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/1.jpg)
2008 EDCLesson12- " , Raj Kamal, 1
EDC Lesson 12: Transistor and FET Characteristics
LessonLesson--12: 12: MOSFET (enhancement MOSFET (enhancement and depletion mode) Characteristics and depletion mode) Characteristics
and Symbolsand Symbols
![Page 2: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/2.jpg)
2008 EDCLesson12- " , Raj Kamal, 2
1. Metal Oxide Semiconductor Field Effect 1. Metal Oxide Semiconductor Field Effect Transistor (MOSFET)Transistor (MOSFET)
![Page 3: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/3.jpg)
2008 EDCLesson12- " , Raj Kamal, 3
Types of FETsTypes of FETs
The family of FETs may be divided into : Junction FET Depletion Mode MOSFET Enhancement Mode MOSFET
![Page 4: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/4.jpg)
2008 EDCLesson12- " , Raj Kamal, 4
Remember JFET Definition
•JFET is a unipolar-transistor, which acts as a voltage controlled current device and is a device in which current at two electrodes is controlled by the action of an electric field at a reversed biased p-n junction.
![Page 5: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/5.jpg)
2008 EDCLesson12- " , Raj Kamal, 5
MOSFET Definition
• MOSFET Field effect transistor is a unipolar-transistor, which acts as a voltage-controlled current device and is a device in which current at two electrodes drain and source is controlled by the action of an electric field at another electrode gate having in-between semiconductor and metal very a thin metal oxide layer .
•
![Page 6: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/6.jpg)
2008 EDCLesson12- " , Raj Kamal, 6
nn--channel depletion channel depletion MetalMetal--OxideOxide--Semiconductor FET (MOSFET)Semiconductor FET (MOSFET)
n channelp
![Page 7: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/7.jpg)
2008 EDCLesson12- " , Raj Kamal, 7
pp--channel depletion channel depletion MetalMetal--OxideOxide--Semiconductor FET (MOSFET)Semiconductor FET (MOSFET)
p channeln
![Page 8: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/8.jpg)
2008 EDCLesson12- " , Raj Kamal, 8
Effect of Insulating SiO2 (metal-oxide) layer
• MOSFET Very high input impedance due to SiO2 layer compared to even reverse biased p-n junction depletion region input impedance in JFET
![Page 9: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/9.jpg)
2008 EDCLesson12- " , Raj Kamal, 9
nn--channel depletion regionchannel depletion region
![Page 10: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/10.jpg)
2008 EDCLesson12- " , Raj Kamal, 10
nn--channel depletion region (normally ON)channel depletion region (normally ON)
![Page 11: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/11.jpg)
2008 EDCLesson12- " , Raj Kamal, 11
Transfer Characteristics of nTransfer Characteristics of n--channel channel depletion region MOSFETdepletion region MOSFET
![Page 12: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/12.jpg)
2008 EDCLesson12- " , Raj Kamal, 12
There is a convenient relationship between IDSand VGS.
Beyond pinch-off
Where IDSS is drain current when VGS= 0 and VGS(off) is defined as –VP, that is gate-source voltage that just pinches off the channel.
The pinch off voltage VP here is a +ve quantity because it was introduced through VDS(sat).
VGS(off) however is negative, -VP.
2
)(
1
offGS
GSDSSDS V
VII
![Page 13: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/13.jpg)
2008 EDCLesson12- " , Raj Kamal, 13
pp--channel depletion MOSFETchannel depletion MOSFET
![Page 14: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/14.jpg)
2008 EDCLesson12- " , Raj Kamal, 14
pp--channel depletion MOSFET (Normally ON at channel depletion MOSFET (Normally ON at VGS = 0)VGS = 0)
![Page 15: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/15.jpg)
2008 EDCLesson12- " , Raj Kamal, 15
2. Enhancement Mode MOSFETS2. Enhancement Mode MOSFETS
![Page 16: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/16.jpg)
2008 EDCLesson12- " , Raj Kamal, 16
nn--channel enhancement mode MOSFETchannel enhancement mode MOSFET
![Page 17: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/17.jpg)
2008 EDCLesson12- " , Raj Kamal, 17
nn--channel enhancement mode Normally Offchannel enhancement mode Normally Off
![Page 18: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/18.jpg)
2008 EDCLesson12- " , Raj Kamal, 18
Note that with a n-channel device we apply a +ve gate voltage to allow source-drain current, with a p-channel device we apply a -ve gate voltage.
n-channel enhancement mode
p-channel enhancement mode
![Page 19: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/19.jpg)
2008 EDCLesson12- " , Raj Kamal, 19
pp--channel enhancement MOSFETchannel enhancement MOSFET
![Page 20: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/20.jpg)
2008 EDCLesson12- " , Raj Kamal, 20
pp--channel enhancement MOSFET (normally channel enhancement MOSFET (normally OFF)OFF)
![Page 21: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/21.jpg)
2008 EDCLesson12- " , Raj Kamal, 21
3. Enhancement Mode MOSFETS in detail 3. Enhancement Mode MOSFETS in detail
![Page 22: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/22.jpg)
2008 EDCLesson12- " , Raj Kamal, 22
Basic MOSFET (nBasic MOSFET (n--channel) Enhancement modechannel) Enhancement modeWhen VGS = 0, the n-channel is very thin and channel width enhances with
+ VGS
![Page 23: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/23.jpg)
2008 EDCLesson12- " , Raj Kamal, 23
Channel width enhancement with +VChannel width enhancement with +VGSGS
The gate electrode is placed on top of a very thin insulating layer.
There are a pair of small n-type regions just under the drain & source electrodes.
If apply a +ve voltage to gate, will push away the ‘holes’ inside the p-type substrate and attracts the moveable electrons in the n-type regions under the source & drain electrodes.
![Page 24: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/24.jpg)
2008 EDCLesson12- " , Raj Kamal, 24
Enhancement mode MOSFET Increasing the +ve gate voltage pushes
the p-type holes further away and enlarges the thickness of the created channel.
As a result increases the amount of current which can go from source to drain — this is why this kind of transistor is called an enhancement mode MOSFET.
![Page 25: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/25.jpg)
2008 EDCLesson12- " , Raj Kamal, 25
Subthreshold region in nSubthreshold region in n--chennel enhancement mode chennel enhancement mode
ID= k exp (qVGS/kBT) where T temperature iu in Kelvin, is Boltzman constant
![Page 26: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/26.jpg)
2008 EDCLesson12- " , Raj Kamal, 26
Subthreshold region in nSubthreshold region in n--chennel enhancement mode chennel enhancement mode
ID= k (VGS VT)2
![Page 27: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/27.jpg)
2008 EDCLesson12- " , Raj Kamal, 27
Above Threshold Above Threshold –– ON stateON state
ID= k (VGS VT)2 =
0.278 (VGS VT)2 mA
0 1 5432 876
ID
VGS
If ID (on) = 10 mA and
VGS = 8 V, then k =10 mA/(8V 2V)2 = 0.278 mA/V2
VT = 2 V
![Page 28: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/28.jpg)
2008 EDCLesson12- " , Raj Kamal, 28
Above Threshold Above Threshold –– ON stateON state
ID= k (VGS VT)2 = 0.278 (VGS VT)2 mA
If ID (on) = 10 mA and
VGS = 8 V, then k =10 mA/(8V 2V)2 = 0.278 mA/V2
VT = 2 VID= k (VGS VT)2
![Page 29: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/29.jpg)
2008 EDCLesson12- " , Raj Kamal, 29
Ideal Output Characteristics of MOSFETIdeal Output Characteristics of MOSFET
![Page 30: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/30.jpg)
2008 EDCLesson12- " , Raj Kamal, 30
Ideal Output linear region before saturation Ideal Output linear region before saturation Characteristics of MOSFETCharacteristics of MOSFET
![Page 31: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/31.jpg)
2008 EDCLesson12- " , Raj Kamal, 31
Ideal Output Saturation formula of enhancement Ideal Output Saturation formula of enhancement mode MOSFETmode MOSFET
chang
![Page 32: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/32.jpg)
2008 EDCLesson12- " , Raj Kamal, 32
Transfer Characteristics in above threshold region Transfer Characteristics in above threshold region and saturation region in nand saturation region in n--channel enhancement channel enhancement
modemode
7 V6 V5 V4 V3V
VGS = VT = 2V
![Page 33: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/33.jpg)
2008 EDCLesson12- " , Raj Kamal, 33
Transfer Characteristics in Subthreshold region and Transfer Characteristics in Subthreshold region and saturation region in nsaturation region in n--channel enhancement modechannel enhancement mode
![Page 34: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/34.jpg)
2008 EDCLesson12- " , Raj Kamal, 34
4. Symbols of depletion and Enhancement 4. Symbols of depletion and Enhancement Mode MOSFETSMode MOSFETS
![Page 35: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/35.jpg)
2008 EDCLesson12- " , Raj Kamal, 35
Symbol of depletion mode MOSFETSymbol of depletion mode MOSFET
n-channel Depletion Mode MOSFET
p-channel Depletion Mode MOSFET
![Page 36: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/36.jpg)
2008 EDCLesson12- " , Raj Kamal, 36
Symbol of enhancement mode of MOSFETSymbol of enhancement mode of MOSFET
n-channel Enhancement Mode
MOSFET p=channel Enhancement Mode MOSFET
![Page 37: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/37.jpg)
2008 EDCLesson12- " , Raj Kamal, 37
SummarySummary
![Page 38: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/38.jpg)
2008 EDCLesson12- " , Raj Kamal, 38
We learnt• Definitions of MOSFET • n-channel and p-channel Depletion
MOSFET normally ON, Pinch off on –VGS in n-MOSFET and + VGS in p-MOSFET
• n-channel and p-channel enhancement MOSFET normally OFF, below Threshold and above VT on + VGS in n-MOSFET and - VGS in p-MOSFET
![Page 39: MOSFET details](https://reader033.fdocuments.us/reader033/viewer/2022042502/55cf9448550346f57ba0e65b/html5/thumbnails/39.jpg)
2008 EDCLesson12- " , Raj Kamal, 39
End of Lesson 12End of Lesson 12