The document discusses MOSFETs and their DC analysis. It covers the basics of MOSFET operation and construction of n-channel enhancement mode MOSFETs. It describes the ideal and non-ideal voltage-current characteristics of MOSFETs including finite output resistance, body effect, subthreshold conduction, and temperature effects. It also discusses common MOSFET configurations like common source circuits and their load lines and modes of operation as well as constant current source biasing.

1. Electronic Devices and
Circuits
UNIT-II
MOSFET& its DC Analysis
By
Asst.Prof.Ms M B Mulik
SITCOE
1

2. Teaching Methodology Detailing
Lecture
No.
Topic Books Page No.
1. Basics of MOS Transistor Operation,
Construction of n-channel E-MOSFET
T2:
Donald Neaman,
“Electronic Circuit
Analysis and
Design”,3rd Edition,
Tata Mc Graw Hill.
120-123
2. E-MOSFET characteristics & parameters 124-128
3.
4.
Non-ideal voltage current characteristics
viz.
1. Finite output resistance,
2. Body effect
3. Sub-threshold conduction
4. Breakdown effects
5. Temperature effects.
136-139
5. Common source circuit, Load Line &
Modes of operation
140-142
149-150
6.
7.
Common MOSFET configurations: DC
Analysis
151-153
8. Constant current source biasing 704-706
and 708

3. Transistor
BJ
T
IGBTFE
T
JFET MOSFET
DMOSFET EMOSFET

4. Basics of MOS Transistor Operation, Construction
of n-channel E-MOSFET

7. Before electron inversion layer
formed
After electron inversion lay
formed
Equivalent circuit

8. Basic Transistor Operation
6/10/2016

9. Current Versus Voltage Characteristics: Enhancement-Mode n MOSFET

10. Symbols for n-Channel Enhancement-Mode
MOSFET

11. Neamen Microelectronics, 4e Chapter 3-12
McGraw-Hill
Symbols for P-Channel Enhancement-Mode
MOSFET

12. Symbols
E-MOSFET characteristics & parameters
MOSFET
Non saturation region VDS<VDS(sat)
saturation region VDS>VDS(sat)

13.  Non Saturation or triode region:
VDS< VDS(sat)
 Saturation or triode region:
VDS> VDS (sat)
E-MOSFET characteristics & parameters
MOSFET
 2
2
TNgs
oxn
D VV
C
L
W
i 







   22
'' TNgsnTNgsnD VVKVVk
L
W
i 
])(2[
2
DSGSTNGSnD VVVVKi 
L
Wk
ParameterConductionK
n
n 
2
,
ox
ox
ox
t
C



14. Non-ideal voltage current characteristics
1. Finite output resistance ( in Saturation Region)
2. Body effect
3.Sub-threshold conduction
4. Breakdown effects
5.Temperature effects.

15. Non-ideal voltage current characteristics
1. Finite output resistance ( in Saturation Region):

16. Non-ideal voltage current characteristics
1. Finite output resistance ( in Saturation Region):
  )1...().........1(
2
DSTNGSQnD VVVKi 
 = Channel Length Modulation Parameter
From above graph the : For ID=0; 0)1(  DSV
VDS= - 1/
VDS=-VA
tConsVDS
V
i
ro
DS
D
tan|)( 1



 
  12
][ 
 TNGSQn VVKro 
By diff. of equation 1 w.r.to VDS
)2.......(..........
1
][ 1
DQ
A
DQ
DQ
I
V
I
Iro  



17. 2. Body Effect
When two transistors are conducting, None zero drain-to- source voltage on M1
 Source M2 is not at same potential as the substrate
These bias condition means that a reverse – bias voltage exits across source –
Substrate PN junction
 Change in Source –Substrate junction voltage that change in Threshold voltage
 This is called the body effect.

18. 3. Subthreshold Condition
 2
TNgsnD VVKi 
Taking Square root on both side
)( TNGS VVKnid 
id Is linear function of VGS
As VGS< VTN : Id is not zero which is
called
sub threshold conduction
Significant power dissipation may take
place for non conduction of more no. of
MOSFET on IC.

19. 4. Break down Effects
 Drain to Substrate PN junction may break down if applied voltage is
too High.( Avalanche Breakdown)
 Punch Through Effect – When drain voltage is large enough for the
depletion region.
 Near Avalanche or Snapback Break down – These are due to second
order effects within the MOSFET.

20. 5. Temperature Effects
 VTN and KN are function of temperature
 Magnitude of VTN decreases as Temperature increases and ID increases for the
applied VGS
 Kn is directly preoperational with Mobility of charge carrier in an inversion layer.
 As temp. increase the charge carrier starts vibrating which reduces their mobility.
 Kn reduces and drain current reduces
 Temp. depends of Kn is more as compared to VTN and overall ID reduces for
applied VGS
 The above action produces the negative feedback condition in MOSFET.

21. Common source circuit, Load Line & Modes of
operation

22. Common MOSFET configurations: DC
Analysis